1. Two hundred cases of nephritis have been investigated. All these cases were admitted to Craigleith hospital as definite cases of nephritis. 2. Modern tests for renal efficiency have been compared. For reasons stated on pages 27-30 the urea concentration test of Maclean and De Wesselow was found to be the most reliable and best suited for use by a general practitioner. 3. Cases of albuminuria with no haematuria, no casts in the urine, no cardiovascular changes and satisfactory renal efficiency as evidenced by the urea concentration of the urine and the diastatic test were regarded as functional. 4. Of the 200 cases 25 were found to be functional according to these criteria; 81 were found to be due to actual nephritis; in 35 the albuminuria was apparently a sequela of or concomitant with cardio. vascular disease; in 13 the albuminuria appeared to depend on tuberculosis of the kidney or lung; in 23 the albuminuria seemed to be dependent on a number of diverse conditions; in 23 there was no evidence of albuminuria. 5. The incidence of the conditions varied according to the age group of the patients. (a) In the second group (31-40) there was a higher proportion of functional cases. It was lowest in the fourth group. (b) In the second group (31-40) there was a higher proportion of actual nephritis. (o) In the fourth and oldest group there was the highest incidence of cardiovascular cases. (d) In the third group (41-50) there was the highest incidence of patients in which no albuminuria or other evidence of disease was obtained. 6. An analysis of the 81 cases of actual nephritis has been made with a view of enquiring into their etiology. (a) A positive Wassermann reaction was obtained in 7.4% of the 81 actual nephritis cases, whilst it was obtained in 10% of the total number of oases. Thus the percentage in the nephritis cases was less than the percentage of all the cases. (b) It is remarkable that 44% of all cases examined and 57% of the actual nephritic cases attribute their nephritis to exposure but it is open to question whether this opinion may not be biased by the patients views as to entitlement to pension. As all these patients were ex- service men there can be no doubt that the exposure to which they were subjected was severe and often prolonged. (c) There is no evidence to support the view that age, previous occupation, or length of service with the colours were of etiological significance. (d) There is no satisfactory evidence that hyper - chlorination of the drinking water or any of the possible factors discussed on pp.55 m 70 had anything to do with nephritis. (e) The curious heavy incidence among troops in the trenches as compared with those in base depots, and in troops who came into contact with men from the line suggests that an unknown causal agent may have been carried by lice. 7. Should a patient recover from an acute attack of nephritis one of three things may hapren. Firstly, he may recover completely, in which case no further signs or symptoms of renal disease will be elicited; or, secondly, the recovery may be almost complete and yet the patient may remain subject to frequent relapses of sub -acute nephritis; or, thirdly, the condition may become chronic and progress in a slow insidious manner. In all probability the second second and third possibilities will go on until a granular kidney results. 8. Since surgical operations in connection with these cases so frequently give bad results, the patient often dying of uraemia, it is necessary to know the renal efficiency before operative treatment is undertaken. Now, the renal efficiency can be quickly and approximately gauged by the urea concentration test. Two patients were operated upon for renal calculus, one for tuberculous kidney and one for urethral stricture. All these patients gave a satisfactory renal efficiency and all came through the operation successfully except the last -named who died from septicaemia.