Acetaminophen (APAP) and gentamicin are widely used for many patients, but little in-formation is available regarding the combined effects of APAP and gentamicin. This study was aimed to investigate the potent nephrotoxicity following combined-treatment with APAP and gentamicin. Serum biochemical parameters and histopathological changes in the kidney were observed in female SD rats after continuous daily treatment with either 600 mg/kg/day APAP, and/or 300 mg/kg/day gentamicin for 3 days, and compared with saline sham-treated control animals. APAP and gentamicin combination-treated rats exhibited inconsistent increasing tendency in blood urea nitrogen (BUN) by 96 hours after the last treatment, compared to control or the animals treated with each drug. The relative kidney weights were also increased. Histopathological findings of kidneys revealed that necrosis of proximal convoluted tubules were higher in rats treated with APAP and gentamicin combination than the rats treated with each drug alone. These results suggest that combination use of both drugs have more severe nephrotoxicity than treating each drug alone.