One hundred eighty four patients with advanced inoperable non-small cell lung cancer were treated with either lonidamine (A), mitomycin-C/vindesine (B), or mitomycin-C/vindesine plus lonidamine (C) in a prospective randomized trial. The response rates for each treatment arm were 3.4% (A), 22.4% (B) and 25.9% (C), respectively. This difference is statistically significant (P less than 0.01). The median survival time for patients treated with mitomycin-C/vindesine and mitomycin-C/vindesine plus lonidamine was 194 days and 221 days, respectively. In comparison with 145 days for lonidamine alone there is a statistically significant difference in survival between the chemotherapy groups (P less than 0.01). When combined with mitomycin-C/vindesine, lonidamine induces an increase in the response rate and there is a higher proportion of patients living after 12 months of treatment (32% v 20%) in comparison to mitomycin-C/vindesine alone. The subjective tolerance of all treatment groups was very good, toxicity was only mild without major differences between the treatment arms. Combination chemotherapy with mitomycin-C/vindesine plus or minus lonidamine could prolong survival in advanced inoperable nonsmall cell lung cancer significantly without severe toxicity.