The seventh pandemic of cholera reached Madagascar in March 1999. In 15 months of dissemination, 31,095 people were infected, 5.8% of whom died. The first case in Madagascar was recorded in Tamatave (the second largest city and the island's main port, on the east coast) on February 29 2000. The health services of the district responded efficiently to the crisis. We carried out an epidemiological investigation to determine the characteristics of the outbreak in Tamatave. We retrospectively studied the records of patients consulting for diarrhea at the health centers of Tamatave from February 29 to June 30 2000. We defined cholera cases according to the recommendations of the World Health Organization for international notification. We recorded the date of diagnosis, sex, age, address, main clinical symptoms, treatment and outcome. Statistical analysis was carried out with Epi Infor 5.01b software. During the 123 days of the study, we recorded 356 cases of cholera, 5 of whom died (attack rate = 2.5 per thousand, case fatality rate = 1.4%). The median age of the patients was 27 years and 8 months and the sex ratio was 1. The attack rate was highest for men aged over 50 years. Severe clinical signs were observed in one sixth of the cases. Men aged 15 to 29 years and 30 to 49 years presented more severe disease than women of the same age (relative rates of 3.6 and 5.9 respectively, p < 0.01). Cholera may become endemic in this province following this outbreak. It may be difficult to stop the spread of cholera within a country but appropriate organization of the medical structure and staff and training in cholera management may decrease the rate of mortality due to this disease.