The epidemiology of the disease is not compatible with direct transmission. Parasites were present in the circulating blood of 91% of cases. The dist. of Phlebotomus perniciosus in Italy coincides very closely with that of kala azar, that of P. papatasii is wider than that of the disease, that of P. major more restricted. P. perniciosus, P. major, P. papatasii and P. sergenti were fed on a Chinese hamster infected with Leishmania in-fantum. The infection rates were 96.8%, 92.3%, 3.5%, and nil, respectively. P. papatasii fed on bone marrow which showed 1 parasite to 40 fields was not infected. 4 out of 63 P. perniciosus fed on 5 cases of kala azar were infected, as was 1 out of 751 caught in or near kala azar houses. Out of 130 P. papatasii fed on 6 cases of kala azar, none were found infected with Leishmania. 15 P. perniciosus were placed in a Hertig apparatus after the infecting feed on a Chinese hamster and in 6 instances flagellates were recovered from the capillary of the Hertig apparatus. The local race of P. major is a possible carrier, but its bionomics and dist. indicate that P. perniciosus is the main carrier. The visceral Leish-manias appear to be particularly adapted to sandflies of the major group.[long dash]Phlebotomus macedonicus* (p. 468), Macedonia, P. canaaniticus* (p.468), Palestine, and P. major var. syriacus* (p.467), Syria and Palestine, are described. The dist. of the major group in relation to that of Mediterranean kala azar is described. P. macedomcus is considered the most likely carrier in Macedonia; an unknown sp. of the major group, in the Sudan. In Cricetulus griseus, Cricetus auratus, and Microtus guntheri infected with L. injantum no cutaneous ulcers developed although the skin was heavily infected; there was no permanent periarthritic swelling; parasites were rare in the general circulation; and the visceral infection did not disappear spontaneously. [long dash]In Catania the gecko Tarentola mauretanica was free from Leishmania infection and could not be inoculated. P. minutus and L. tarentolae are both absent in Catania and both present in Tunis and Algeria. 17 out of 49 specimens of T. mauretanica were infected with Trypanosoma ptyodactyli, and P. parroti and P. papatasii became infected by feeding on geckos. Since P. papatasii, apparently, does not feed on geckos in nature, P. parroti is probably the carrier of Trypanosoma ptyodactyli.