_Clinical Diagnosis._—Cases of kala-azar are usually diagnosed as malaria and it is in the lack of response to quinine that we have our best point of differentiation. In children showing splenomegaly the probability of the case being kala-azar rather than malaria is indicated if the case has shown progressive deterioration of health. Malta fever shows a rather similar succession of febrile and afebrile periods but the spleen of the former rarely shows marked enlargement and the bronchial catarrh, sweatings, transient joint swellings and neuralgic manifestations are characteristic of Malta fever. Kala-azar may show muscular pains and slight sweatings and the differentiation has at times only been made by the laboratory diagnosis. Typhoid and the paratyphoids are best differentiated clinically by the presence of a continued fever, the absence of a double daily rise and the existence of a more marked apathy. The recent statements that hookworm disease may show enlargement of the spleen would make this a condition to differentiate. Hookworm ova and an eosinophilia indicate ancylostomiasis but there is always the question here as with malaria as to the existence of kala-azar and some other affection. _Laboratory Diagnosis._—The leukemias can be easily differentiated by the blood picture, an important matter because the spleen of spleno-myelogenous leukemia is very friable and the danger from splenic puncture is far greater in this condition than in kala-azar. Banti’s disease with its leucopenia shows a rather similar blood picture and can only be surely differentiated by the finding of leishman bodies in kala-azar. While malaria may at times show a leucopenia below 4000, a polynuclear percentage below 50 and a large mononuclear one of 20 or more, yet the simultaneous appearance of all three is rare in malaria while common in kala-azar. Malta fever, typhoid and the paratyphoids are best differentiated by blood cultures or agglutination tests. Until recently it was recommended that for diagnosis our best procedure was to make a splenic puncture. Manson and others have pointed out the dangers from splenic puncture in kala-azar and have rather preferred puncture of the liver, although recognizing that the chances of obtaining parasites from a liver puncture, are less than from a splenic one. Statistics have been given where a mortality approximating 1% has followed spleen puncture. Bousfield, however, using an all-glass syringe with a 1½ inch needle did not have a fatality in 120 spleen punctures. For diagnosis the spleen or liver juice, rather than pure blood, is smeared on a slide and stained by some Romanowsky method, preferably that of Giemsa. Cultures on N. N. N. medium can also be made. Human blood seems to inhibit growth so that N. N. N. medium for cultivating _Leishmania_ should be made from rabbit blood.