A total of 26 evaluable patients with previously untreated, non-resectable adenocarcinoma of the lung were given 80 mg/m2 i.v. teniposide daily for 5 days every 3 weeks. Three partial responses (11%) were obtained that lasted for 12, 11 and 32 weeks, respectively. Leucopenia was the dose-limiting side effect, with WBC counts of less than 2 x 10(9)/l being observed in 42% of patients, resulting in one septic death. At the dose and schedule used in the present study, teniposide showed only limited activity in adenocarcinoma of the lung.