An epidemiological investigation into Newcastle disease in village poultry farming was carried out for 12 months (from May 1999 to June 2000) in Ambohimangakely and Moramanga, two agro-ecologic zones of Madagascar. The thirty families that were surveyed stated that they had incurred losses from an epizootic with high mortality rates at least once prior to the investigation. The results of serological tests and virus isolation showed that the disease, responsible for 44.3% of all the mortality recorded during the twelve-month period, was Newcastle disease. Maximum incidence of the disease (71%), affecting 75% of the families, occurred in October 1999, and seroprevalence often reached 100% after the outbreak had ended. The infection was brought to the villages either by newly introduced hens or recovered birds. All forms of Newcastle disease (epidemic, endemic and asymptomatic) were observed. The way farmers reacted contributed to the spread of the virus within a village and to neighbouring locations.