Epidemiological aspects on an outbreak of cholera at North Sumatra Province, Indonesia, in 1978 and 1979 were analyzed. The epidemic started at Nias island on March 1978, spread to the main area of the province until the beginning of 1979 and returned to Nias along the highways. A total of 23,900 cases of clinical cholera was reported in which 1,110 died by the 30th week of 1980. Vibrio cholerae eltor Ogawa strains were isolated from the cases reported in 1978 while eltor Ogawa and Inaba strains were isolated in 1979.