OBJECTIVES: Paclitaxel(Taxol) si a chemotherapeutic agent with potent microtubule stabilizing activities that arrests cell cycle in G2-M. Since D2-m is the most radiosensitive phase of the cell cycle, paclitaxel has potential as a cell cycle-specific radiosensitizer. This study was designed to investigate the effects of paclitaxel to radiotoxicity in normal rat liver. MATERIALS & METHODS: A single intraperitoneal infusion of paclitaxel(10mg/kg), and a single irradiation(8Gy, x-ray) to the whole abdomen, and combination of irradiation(8Gy,x-ray)24 hours after paclitaxel infusion were done in Sprague-Dawley rats. The incidence of mitosis, apoptosis and parenchymal changes of the liver were evaluated at 6 hours, 24 hours, 3 and 5 days, respectively. RESULTS: Paclitaxel and irradiation significantly increased mitosis at 6 hours and apoptosis was increased by irradiation at 6 and 24 hours. Increased numbers of apoptosis at 3 days by paclitaxel alone was not significantly different from control. Combination of paclitaxel and irradiation showed significantly increased numbers of mitosis and apoptosis at 6 hours. The degree of necrosis of hepatocyte was not significantly different between 3 groups. CONCLUSION: Since the incidence of mitosis, apoptosis and hepatocyte necrosis were not increased by paclitaxel infusion 24 hours before irradiation, paclitaxel did not show radiosensitizing effect in this experimental condition. Studies with conditions similar to clinical situation will be the next stop to define the radiosensitizing effects of paclitaxel.