Sixty-six patients with advanced solid tumors were treated with 4'-epi-doxorubicin at a dose of 90 mg/m2 by rapid IV injection every 21 days until the disease had progressed or to a maximum cumulative dose of 540 mg/m2. Myelosuppression, nausea and vomiting, and alopecia were the almost frequent side effects, but their incidence seemed lower than that after a comparable dosage of doxorubicin. After a cumulative dose of 540 mg/m2 a significant decrease of QRS complex deflection on the electrocardiogram was detected, but no case of congestive heart failure was observed. Partial remission and minor remission were achieved, respectively, in nine (15%) and five (9%) out of 59 evaluable patients for a median duration of 6 months. Partial remission occurred in anthracycline-sensitive tumors like breast cancer (4 of 13), lung cancer (1 of 17), head and neck cancer (1 of 8), gastric cancer (2 of 4), and ovarian cancer (1 of 1).