In toxicity studies, it is important to select a vehicle that does not affect the toxicity assessment of the test substance. To obtain toxicity information on corn oil as a Vehicle for subcutaneous toxicity studies of non-aqueous test substances, Crl:CD (SD) rats (6 animals/sex/group) were repeatedly dosed with corn oil at 0 (negative control; saline), 1, 2 and 5 mL/kg/day for 4 weeks. High body weight due to retention of the administered substance were found in corn oil groups in both sexes at 2 mL/kg/day or higher. Some relative organ weights at 2 mL/kg/day or higher were decreased due to high body weight or body weight gain. Subcutaneous retention of the administered substance found in all corn oil-treated groups at necropsy was observed on histopathological analysis as accumulation of the administered substance and granulation tissue. Accumulation of the administered substance in inguinal skin, the axillary lymph node, and alveolus of the lung and bronchus was observed. Multiple white nodules in the abdominal cavity and liver observed in a female at 5 mL/kg/day at necropsy were considered to be related to lipogranuloma at the peritoneum and hepatic capsule. In hematology, RBC was lower in females at the 5 mL/kg/day than in the control group.. In conclusion, since the effects of corn oil administration were found in groups at all volumes, it is necessary to take into account that corn oil induces these changes when used as a vehicle of a test substance in toxicity studies.