This study was designed to determine the bioavailability of etoposide capsules administered orally at doses of 50 and 75 mg. Patients with inoperable or relapsed lung cancer, who had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 and adequate organ function, were eligible. A group of 17 patients were evaluable, all of whom were 75 years old or less, with an ECOG performance status of 0 or 1. The bioavailability of oral etoposide was determined by measuring the area under the etoposide plasma concentration versus time curve (AUC) on days 1, 10 and 21 during a once-daily regimen of oral administration for 21 consecutive days and comparing the value with the AUC achieved following intravenous administration 1 or 2 weeks after the last oral dose. The bioavailability of 50, 75 and 100 mg oral etoposide was determined in six, nine and two patients, respectively. The mean etoposide bioavailabilities (+/- SD) of the 50-mg and 75-mg doses were 47 +/- 11% and 59 +/- 18%, respectively, and of the 100-mg dose in two patients were 51% and 33%, respectively. There was no statistically significant difference in bioavailability between the 50-mg and 75-mg doses. The bioavailability of low-dose oral etoposide was the same as that reported in previous higher dose oral etoposide bioavailability studies and that shown on the package insert supplied by the manufacturer. Improved bioavailability of low-dose oral etoposide was therefore not observed in a population of Japanese patients.