A cross-sectional study was carried out in 216 randomly selected, representative rural villages in the northeastern part of Ghana from March 1995 to May 1998. Inhabitants of randomly selected households, stratified by age and gender, were included. The geographical position of villages was recorded with a global positioning system (GPS). The prevalence of Oesophagostomum, hookworm and Strongyloides stercoralis infections in a study population of 20 250 people was determined by microscopic examination of larvae in stool cultures. The overall prevalence was 10.2, 50.6 and 11.6% for the three nematodes, respectively. Hookworm infections were seen in all but one (99.5%) and S. stercoralis in 88.4% of the 216 villages, while Oesophagostomum infections were found to be common in a limited area with prevalences varying from 0 to 75%. An association was found between Oesophagostomum and hookworm infection, both at the individual and at the village level. Spatial analysis of the prevalence data indicated that the endemic area is relatively clearly demarcated to the south of the study area.