We performed a randomized study from February 1979 to August 1981 in patients with small-cell lung cancer (SCLC) with the aim of defining the potential advantages of replacing vincristine (VCR) with vindesine (VDS), at that time a new semisynthetic vinca alcaloid, in the classical two-drug combination cyclophosphamide (CTX)-VCR. A total of 116 previously untreated patients were admitted to the study. Of 104 patients evaluable for response, 49 had limited disease and 55 extensive disease. Patients received 10 mg/kg CTX i.v. on days 1-4 and either 1 mg VCR i.v. or 2 mg/m2 VDS i.v. on days 1 and 4, and repeatedly every 4 weeks for 12 courses. In addition, the patients with limited disease received split-course radiotherapy (30 Gy/10 F, 3 or 5 weeks rest, 25 Gy/10 F, total treatment time 7 or 9 weeks) to the primary tumor, the mediastinum, and the supraclavicular areas between the second and third cycles of chemotherapy. The response rate to the first two chemotherapy cycles was 47% (4 complete response [CR] and 22 partial response [PR]) to CTX-VCR and 47% (4 CR and 19 PR) to CTX-VDS. Subsequent to radiotherapy the response rate increased to 93% for CTX-VCR and 100% to CTX-VDS, respectively, in the patients with limited disease. Local recurrence and/or progression occurred in 49% of limited disease responders and in 96% of extensive disease responders. In responders with limited disease, the first site of relapse was loco-regional in 25% for the VDS group as opposed to 15% in VCR group. In the patients with extensive disease, the corresponding figures were 62% for the VDS and 50% for the VCR group. Median duration of remission in all patients treated with CTX-VCR was 132 days compared to 203 days in the CTX-VDS group (not significant, NS). Median survival was 338 days for CTX-VCR vs. 342 for CTX-VDS in patients with limited disease, and 214 days for CTX-VCR vs. 312 days for CTX-VDS in extensive disease (NS). One-year survival figures were 47% for CTX-VDS and 35% for CTX-VCR patients. Two-year survivals were 4 and 9%, respectively. Neurotoxicity was the main toxic manifestation in both treatment groups. Severe peripheral neuropathy (grade 4, World Health Organization [WHO]) did not occur with either drug regimen. Treatment was discontinued because of grade 2-3 neuropathy in one patient after 6 cycles of CTX-VCR and in five patients after 1-6 cycles of CTX-VDS.(ABSTRACT TRUNCATED AT 400 WORDS)