Twenty-five patients with histologically proven malignant mesothelioma participated in a trial of imatinib mesylate (Glivec) with a starting dose of 400 mg per day taken orally, up to a maximal dose of 800 mg. No responses were observed in the patient group, while three patients showed prolonged (>6 months) stabilization of disease. The median survival time was 398 days (range 88-840); the median time to progression was 63 days (range 29-275). Side effects of the medication were mild and included edema, nausea, constipation and diarrhea. We conclude that further investigation with monotherapy imatinib in mesothelioma is not warranted.