Working off and on in fever hospitals since 1897 and for the last two years acting in charge of such institutions here and elsewhere, one has had numerous opportunities of seeing the various forms of diphtheria, and with the hope of learn- ing how far it is possible to make an accurate diagnosis from the clinical features alone, one has chosen a series of 100 cases in which the disease was limited to the upper air passages and 47 - to be first considered - in which the larynx was involved. The value of bacteriology one does not for a moment doubt and indeed practically in every case a bacteriological examination was made, but the cases notified for removal to hospital are, with few exceptions, diagnosed from the clinical signs alone. The difficulty of making a diagnosis from the clinical features is considerable, more especially outside hospital practice, mainly because in many cases a thorough examination is impossible. In hospital a medical man has practically no disadvantages to contend with. He has light, and he has liberty to go into every particular, both of which are often withheld from those outside.