To determine whether the chemotherapy resistance of non-small cell lung cancer could be modified by oral dexverapamil, the D-isomer of verapamil, 54 patients were entered into a randomised phase II study of oral dexverapamil plus chemotherapy (vindesine/etoposide) (arm B) versus chemotherapy (arm A) alone in January 1994. Chemotherapy consisted of intravenous vindesine 3 mg/m2 bolus on days one and five and etoposide 140 mg/m2 on days two and four. Dexverapamil was given for six days, 1500 mg a day divided into six doses of 250 mg every four hours starting 24 h prior to chemotherapy. According to the individual tolerability, the single dose could be increased up to a maximum of 400 mg. Cycles were repeated 3 weekly up to four courses. At this stage of the analysis, 34 patients (18 in arm A and 16 in arm B) are evaluable for toxicity and response. Cardiovascular side effects were more marked in the patient group with dexverapamil. On average, the dose of dexverapamil was 1800 mg a day. There were 5 partial remissions (31.3%) and 9 no changes (56.3%) in the group with dexverapamil as opposed to 2 partial remissions (11.1%) and 6 no changes (33.3%) in the group without dexverapamil. As far as the preliminary results show, the addition of dexverapamil to vindesine/etoposide chemotherapy in this study seems to be associated with improved outcome.