Filariasis is one of the major problems of public health in India, because of the many millions of people who are infected and because practical measures for its control have proved so difficult. The extent of the infection and the difficulties of control have been well shown in the excellent studies carried out under the National Filaria Control Programme, directed from the National Institute for Communicable Diseases at Delhi. This Programme was launched in 1955 and it has constituted the biggest and best sustained antifilarial organization in the world. Most of the statistics quoted in this paper are derived from its reports. It may seem rash for an outsider like the author to speak or write on filariasis in India when there are already many experts in the country who have a more intimate and deeper knowledge of the subject. Nevertheless this rashness has been ventured because filarial infection seems so important for India that attention ought to be drawn to it, on such an occasion as the Jubilee Celebration of the Haffkine Institute when the medical problems of the country are passed, as it were, under review.