24 patients with unresectable non-small cell lung cancer (NSCLC) (14 stage IIIB and 10 stage IV) with a performance status of 70% or higher and without liver metastases received 120-165 mg/m2 epirubicin as an intravenous bolus every 21-28 days up to the maximum cumulative dose of 900 mg/m2. 6 patients (25%) (95% confidence limits 9.8-46.7%) achieved partial remission for a median duration of 7.5 months (range: 3-13+). The median dose actually administered per course was 120 mg/m2 in responsive and non-responsive patients. The dose-limiting side-effect was neutropenia. 1 patient receiving the higher dose died of drug-related infection. Other non-dose-related grade 3 side-effects were alopecia (100%) and vomiting (17%). In 4 patients, the treatment was interrupted because of a greater than 10% reduction in the left ventricular ejection fraction as calculated by radionuclide angiocardiography. None of these patients suffered from cardiac symptoms. The median survival was 10 months (range 1-16). These data suggest that epirubicin at 120-135 mg/m2 may have higher antitumour activity than standard doses in patients with NSCLC. Further studies are needed to clarify whether or not high-dose epirubicin increases, the risk of cardiotoxicity compared to standard doses.