Thirty female pigs, average weight 32 kg, were given fenbendazole for 3 days to test the safety of the drug. Dosages of 0, 3, 9, 15, and 25 mg of active ingredient/kg of body weight were mixed with the feed. Chemical analysis, urinalysis, and hematologic, gross and microscopic pathologic, and bone marrow cytologic examinations revealed no significant adverse effect due to this drug.