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An estimated 250 000 people in northern Ghana and Togo are infected with the intestinal helminth parasite Oesophagostomum bifurcum, as detected by stool cultures. Clinical disease caused by O. bifurcumis responsible for about 50 cases per year at the region's central hospital, and presents as painful abdominal masses: inflammatory colonic nodules containing live juvenile stages of the helminth. In individuals living in villages highly endemic with O. bifurcuminfection, colonic pathology visible by ultrasound is also highly prevalent. These nodules also contain O. bifurcumjuvenile worms but are apparently asymptomatic. Thus, O. bifurcuminfection and asymptomatic colonie pathology are highly prevalent within this area, but clinical disease is relatively uncommon. The natural evolution and regression of the colonie pathology in an endemic community in northern Ghana and its distribution within the population is described. Of the 299 individuals in the study group, 28% had colonie pathology at recruitment in the late-rainy season, which decreased with a half-life of 3–4 months during the dry season. Of those negative at recruitment, 28% developed nodules during the year, the majority appearing at the end of the subsequent rainy season. Children tended to have a higher prevalence and intensity of ultrasound-visible pathology compared to adults. Almost half (49%) of the study group had colonic nodules at least once during the year, and 2 % of these individuals presented with clinical disease to the local hospital during the mid-rainy season.