In November 1996 a yellow fever (YF) outbreak occurred near Kaffrine in the central part of Senegal. Thirty-six deaths were notified, all children under 15 years of age. The YF diagnosis was confirmed by MAC-ELISA or by virus isolation. The immune status against YF virus of a sample population of 449 individuals was determined, and 31 confirmed cases and 69 asymptomatic cases were reported. Distribution of YF cases and incidence rate decreased with age, while the attack rate was stable in all age groups. Larva indices were high and Aedes aegypti was common in all villages, causing man-to-man transmission. The greatest risk of YF disease was lack of immunity, especially in individuals <20 years of age. The outbreak was rapidly controlled by an emergency immunization campaign. YF epidemics occurred in Senegal over two consecutive years. The last outbreak reached the main road to Dakar and the risk of spread to urban areas has increased.