Buflomedil was administered intravenously to rats at dosages of 1, 4, 12 or 30 mg/kg/day for up to three months. The no-adverse-effect dosage was considered to be 12 mg/kg/day. At 30 mg/kg/day several deaths and clinical signs, including ataxia, decreased activity, dyspnea and jerking movements after dosing, were observed. These were considered to result from the acute, exaggerated pharmacologic effects of buflomedil. Body weight gain and food consumption were decreased after six weeks in males at 30 mg/kg/day. Increases in the relative weights of the kidneys, brain and testes of males at 30 mg/kg/day were correlated with decreased body weight gain in this group. There were no effects on hematology or serum chemistry parameters, and no morphologic changes were found.