Recently, it has been established that human infection with Oesophagostomum bifurcum is common in northern Togo and northeastern Ghana. Two surveys were conducted in this area. In a regional survey, O. bifurcum infection appeared to occur in 38 of 43 villages. The highest prevalences (up to 59%) occurred mostly in small isolated villages and were usually associated with high hookworm infection rates. The infection was relatively rare in children under five years of age (7% infected). In older individuals, females showed higher prevalences than males (30% vs. 24%). In a second survey, the entire population of two high-prevalence villages was examined. Infection rates were low in children under three years of age, but rose quickly thereafter, suggesting intense transmission. A stable level of infection was reached by 10 years of age. Oesophagostomum larvae were found more frequently in hookworm-positive than in hookworm-negative coprocultures, and possible explanations for the association between infection with Oesophagostomum and hookworm are discussed.