We measured concentrations of 5-FU in cancerous and normal cervical tissues in 16 patients with cervical cancer to whom UFT or tegafur had been administered. The results were as follows: Concentrations of 5-FU in cancerous tissues measured 30 minutes and 2 hours after UFT administration were 0.181 +/- 0.034 microgram/g and 0.562 +/- 0.145 micrograms/g respectively, while in patients to whom tegafur had been administered, they were 0.105 +/- 0.030 microgram/g and 0.126 +/- 0.015 microgram/g respectively. The comparison of 5-FU concentrations in cancerous tissues within each individual patient indicated that the value was higher after UFT administration than after tegafur administration in 13 cases (81.3%). When classified by histological typing, cases of non-keratinizing carcinoma showed the highest value, followed by keratinizing cases and adenocarcinomas, which indicated the lowest value with administration of UFT. However, there were no differences among these three types when tegafur was administered. Based on the above findings, it was indicated that UFT is an antitumor agent with a higher tumor specificity, especially in non-keratinizing carcinoma.