Twenty-seven evaluable patients with small cell lung cancer (SCLC) resistant to, or relapsed after induction combination chemotherapy (CT) were treated with etoposide (VP16) plus cisplatin (DDP). Previous treatment was: alternating CT with cyclophosphamide (C), adriamycin (A), methotrexate (M), procarbazine (P) (CAMP)/VP16, BCNU (B), hexamethylmelamine (H) (VP16 BH) in 16 patients; C, A, vincristine (CAV) in 6 patients; C, A, and VP16 (CAVP16) in 5 patients. We observed 2 (7%) complete responses (CR) and 9 (33%) partial responses (PR). Duration of CRs was 8 and 14 weeks, respectively. PRs lasted a median of 22 weeks (range 16-44). Seven of 21 (33%) patients previously treated with VP16 responded to DDP plus VP16 (D-V). These results confirm D-V regimen as active in SCLC patients even when heavily pretreated. Our 33% response in patients who had VP16 in their induction treatment regimen provides further evidence of an important potentiating effect of DDP, as reported in animal system.