Malignant thymoma (MT) is a rare tumor that is often associated with myasthenia gravis (MG). This tumor is considered resistant to chemotherapy. We had the opportunity to treat five patients with MT with cyclophosphamide 800 mg/m2, Adriamycin 50 mg/m2, and vincristine 1.4 mg/m2 (CAV) in cycles of 21 days. Two patients with MG that was resistant to antimyasthenic drugs immediately responded to this combination. One patient with only MT had a complete response, and two patients with only MT had a partial response. Two out of the five patients are still alive and free of disease. Two patients died of disease, and one died from a neutropenia-induced respiratory tract infection. It is concluded that this combination chemotherapy is active in MT and MG and deserves additional trials.