The purpose of this presentation is to explain the filariasis problem in British Guiana and to urge the cooperation of residents in the joint research and control program established by the governments of British Guiana and the United States. The work of the Technical Assistance Development Organization (TADO) is described and illustrated in detail. The epidemiological and socioeconomic factors are discussed and the treatment program is described. In this presentation clinical subjects are first presented and their lifestyle is described. The crippling effects of filaria are discussed and demonstrated. The life cycle of the filaria is then described and illustrated, and histologic slides are presented which demonstrate the presence of the parasite in the blood. The diagnostic use of the nocturnal blood smear is described and demonstrated in considerable detail. The program then focuses on the work done by individual doctors, and the later research and control work of TADO is illustrated. The use of posters, pamphlets, lectures, conferences, and discussion groups in efforts to educate the public in the epidemiological and therapeutic aspects of this disease is discussed. The work of the night survey teams that go from house to house collecting blood samples from each member of the family and the work of the epidemiological teams in collecting mosquitoes for examination and spraying breeding places are presented in detail. The therapeutic use of several antihelminthic drugs is also discussed and described.