Gastrointestinal and bronchopulmonary nematode infections and the efficacy of netobimin (Hapasil) were analyzed by way of fecal examination in 10 female mouflons (Ovis musimon), in central Spain, February 1993. Before treatment all 10 mouflons had Trichostrongylus axei, Teladorsagia circumcincta and Marshallagia spp.; sic had Nematodirus spp., two had Trichuris sp., one had Capillaria sp., seven had bronchopulmonary Dictyocaulus filaria and 10 mouflons had protostrongylid lungworms (Muellerius capillaris, Protostrongylus rufescens, Cystocaulus ocreatus or Neostrongylus linearis). Netobimin (7.5 mg/kg) was 100% effective against T. axei, T. circumcincta, Marshallagia spp., and D. filaria infections whereas one animal continued eliminating Nematodirus spp. eggs. The drug also was effective against Capillaria spp. but not against Trichuris spp. or protostrongylid infections.