An introductory study is made of the physiological function of the nose as the first line of defence of the air passages. These consist essentially of an upper part formed by the nose and naso-pharynx and a lower part comprising the larynx, trachea, bronchi and bronchioles. Interference with the proper functioning of the nose may have injurious results in the lower respiratory tract and therefore the interests of the physician and the rhinologist meet on common ground. The ciliary-mucus defence mechanism of the nose is outlined in the case of infective organisms invading the nose and its accessory sinuses. If the defence is overcome the progress of an acute sinusitis is followed and it is shown how in a rigid- walled space such as the antrum, Nature's method of overcoming the infection is by means of re- establishing its drainage and aeration through its natural ostium, and by the attempt at replacement of damaged lining membrane by one having normal ciliated epithelium. It is then shown that in the presence of certain adverse factors in the nose, such as deviated septum, the complete opening of the ostium is interfered with and the infection in the sinus becomes chronic. The sinus now becomes a suppurative focus, giving rise to toxic discharges which pass into the nose and throat, and from which toxic products and bacteria may pass directly into the blood-stream. The maxillary antrum lends itself to study since it is the sinus most often infected and which for a long time may remain the only sinus infected. In addition, its infection often dates from childhood. The rhinologist follows the principle of drainage and aeration whatever his treatment of the sinusitis may be,but in chronic infection he aids the reparative process of nature by removing the diseased)and often disorganised lining membrane, and by making an artificial drainage opening into the nose. This opening is situated nearer the floor of the antrum and is of more favourable size than the natural ostium. Following a short historical review tracing the evolution of the method used, a description of the method of access and drainage is given as embodied in the classical Caldwell-Luc operation with certain modifications such as the high gingivo-labial incision and the formation of a mucosal flap which is laid into the antrum. The method of anaesthesia, and the precautions taken to safeguard the lower respiratory tract it against blood or secretions flowing town into it are outlined. A clinical study then follows of 70 cases of chronic maxillary sinusitis. The local effects are traced to see in how far the procedure succeeded not only in removing the disease and promoting drainage and aeration of the antrum, but also how this was accomplished along the lines of the physiological principles of the nose, so that a healthy nose and antrum may remain. The studies first of all showed that the antrum does not become obliterated after removal of its lining membrane, but retains its form and shape and becomes, in fact; lined with a newly - formed membrane. Support of this finding and reports of the histological examination of this membrane are given from the literature to show that the desired ciliated epithelium is regenerated in 3 to 5 months. When this has occurrred the antral cavity can again assist at its own drainage. The functions of the artificial antronasal opening are outlined by a study of cases where it had closed and it was concluded that it has a primary function of drainage and aeration of the antrum in the first 3 to 5 months before the regeneration of its epithelium after which no ill effects would follow its closure provided no adverse factors are present in the nose that favour re-infection of the antrum in which case its continued use would be highly desirable. It is also shown from cases that where certain adverse factors are present in the nose or recur,the presence of an opening tends to reduce their ill effects on the patient. With reference to cases the optimum size of the opening is discussed in the light of the desired functional results. It is shown that nothing is gained by making . the opening too wide as much of the suction - drainage effect on the antrum would be lost. The role of the mucosal flap is shown to be that of providing a convenient nidus for the outgrowth of new ciliated epithelium into the antrum and secondly of helping to maintain the patency of the antro -nasal opening especially at its important rounded ant.- inferior angle. The effect on the inf. turbinate is studied in the light of its important function of shaping the inspired air -stream in its arched course in the nose and thereby being an integral part in the method of suction - drainage of the accessory sinuses. Interference with this structure at operation should be minimal and even if somewhat enlarged there is a tendency for it to shrink afterwards. In addition, atrophy of the nasal mucosa produced by the old disease often persists giving a roomy nasal chamber where the presence of a reduced inf. turbinate Tould the more disturb the direction and force of the inspiratory air-current. A clinical estimation then follows of the results of this method of drainage on the antral infection and the associated changes it had produced in the nose. The aim of this method and the principles it embodied was to render the patient free of symptoms and gain a normal antrum and nasal cavity free of abnormal secretions. Using this desired result as standard 45.7% of cases were "cured ", 21.4% were "much improved", 14.3% were "somewhat improved" and 18.6% derived no local benefit. The causes for the less favourable results were studied in detail and were shown to be due to certain adverse factors present chief of which were, first and foremost, residual ethmoidal (and sphenoidal) infection and secondly the persistence of the allergic diathesis with recurrence of polypi. The persistence of the latter caused less favourable results in 14.3% of all the cases (or 26.3% of the "uncured "). Where septal deformity was present polypi tended to recur and a poorer result followed. Apart from the further treatment of septal deformities and hypertrophies the patient should receive general medicaltreatrnent directed against the allergic diathesis failing which, the effect of radium application might be tried. Residual ethmoiditis (and sphenoiditis) was the adverse factor present in 20% of all cases (or in 30.7% of the "uncured "). The potential danger of its persistence in causing severe complications after opera tion is stressed. In the "not improved" group it was the factor responsible in 70% of them and its persistence was associated with the persistence of severe types of headache, nasal- discharge and re- infection of antrum and remote symptoms of toxic origin. Methods were discussed to minimise the difficulties attendant on adequately dealing with ethmoidal infection at the time of the antral operation, and amongst others, the transantral method of approach to the ethmoid was discussed, whereby using the usual method of ether anaesthesia both the antrum and the ethmoid could be dealt with through the one approach. The effect of the operation in producing possible damage to the nerve-supply of the teeth and gums and of producing severe swelling or infection of the cheek, or after - neuralgia of the cheek, is studied in this seriesof cases. It was found to be minimal and not sufficient to detract from its superior advantage as a physiological procedure. The effect of the antral treatment on the Rasta chien tube was shown to result in the cure of an appreciable proportion of cases of tinnitus and deafness. In the case of the tonsils only two cases were found where a healthier -looking tonsil resulted afterwards. Tonsil sepsis was still present in 62.8% of all the cases and even if originally caused by antral suppuration sepsis would most likely persist unchanged. The important symptom of headache was present in 60% of cases before treatment and was completely relieved afterwards in half of these and greatly relieved in another quarter. Headache that persisted unchanged was entirely of the frontal type and was largely associated with the presence of septal deformity and ethmoiditis. It was shown that all but 2 cases experienced definite improvement in their general health after operation which pleased them very much even where the local result was not entirely favourable. This occurred after an average interval of 3 months during which the patient's general condition and resistance must be considered, as regards the imposition of further stresses, to be in a "refractory phase".