Abstract 1. 1) Between 1953 and 1956, some 2,000 immigrants came to Israel from Cochin, India. A survey in India in 1954 showed 13.5 per cent. to have clinical signs of filariasis while in Israel, in 1955–1956, 11.6 per cent. had microfilariae in their peripheral blood. The indigenous culex species was shown to be a potential vector. 2. 2) The chain of transmission was broken by: 2.1. a) settlement in areas of low humidity and low mosquito prevalence, mainly in hilly places; 2.2. b) decreasing of crowding by providing adequate housing widely spaced; 2.3. c) mass chemotherapy with diethylcarbamazine (Hetrazan) in three courses of a fortnight's duration. 3. 3) No autochthonous cases have been reported, and a microfilaria survey in 1958 revealed only two carriers in over 1,000 persons examined, representing a drop of 98.5 per cent. in prevalence. 4. 4) The relative values of the various methods of control are briefly discussed and complete eradication envisaged for the near future.