In this study, pharmacokinetics, clinical effects, and toxicity of daily oral etoposide were studied in 12 patients with advanced lung cancers. Administration schedule was 25 mg/body everyday of a 4-week cycle or 50 mg (25 mg twice)/body for 14 consecutive days of a 4-week cycle. The pharmacokinetic parameters of both groups in serum were as follows: 1) mean peak plasma concentration of 0.91 +/- 0.18 micrograms/mL (25 mg) and 1.24 +/- 0.12 micrograms/mL (25 mg twice); 2) elimination half-lives of 6.48 +/- 1.09 hours (25 mg) and 3.64 +/- 0.27 hours (25 mg twice); and 3) the area under the plasma concentration curve of 7.09 +/- 1.26 micrograms.hr/mL (25 mg) and 8.67 +/- 0.77 micrograms.hr/mL (25 mg twice). There was a significant difference between those two schedules in terms of the plasma concentration and the duration at a low concentration (greater than 1 micrograms/mL) of etoposide. Low daily administration of oral etoposide is shown to be well tolerated and easy on the patient. More studies are needed to study whether prolonged schedules of lower doses of etoposide could result in improved prognosis.