In southern Ghana guinea worm disease was found to occur almost exclusively in villages dependent upon pond water during the dry season. The recent occurrence of guinea worm for the first time in many villages in the survey area suggests that the disease is spreading. The risk of increasing disease in the Accra plains is serious, because almost half of the 159 villages surveyed use pond water, and residents frequently travel to endemic areas. In this study adult male farmers were at greatest risk of becoming infected. The average work loss in untreated adults was more than 5 weeks. Because guinea worm disease is seasonal, conciding with peak agricultural activities, and few alternative labor sources are available for the incapacitated farmer, a marked reduction in agricultural output occurs. Additional research is needed to guide health education programs, to evaluate the effectiveness of chemical control of cyclops in ponds, and to develop low-cost improved rural water supplies.