Previous surveys conducted in northern Ghana where Oesophagostomum bifurcum is endemic showed that O. bifurcum-induced nodular pathology could be detected in up to 50% of the inhabitants. The impact of albendazole-based mass treatment to control both infection and morbidity is assessed and compared with the situation in a control area where no mass treatment has taken place. A significant reduction in the prevalence of infection based on stool cultures was achieved following two rounds of mass treatment in one year: from 52.6% (361/686) pre treatment to 5.2% (22/421) 1 year later (χ₁² = 210.1; P < 0.001). At the same time, the morbidity marker of ultrasound-detectable nodules declined from 38.2% to 6.2% (χ₁² = 138.1; P < 0.001). There was a shift from multinodular pathology, often seen in heavy infections, to uninodular lesions. In the control villages where no treatment took place, O. bifurcum infection increased from 17.8% (43/242) to 32.2% (39/121) (χ₁² = 9.6; P < 0.001). Nodular pathology decreased slightly from 21.5% to 19.0%, but a higher proportion of these subjects developed multinodular pathology compared with baseline (χ₁² = 5.5; P = 0.019). It is concluded that repeated albendazole treatment significantly reduces O. bifurcum-induced morbidity.