Toxicity and response rates are evaluated in a randomized phase II study comparing paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ)/cisplatin with teniposide/cisplatin in the treatment of non-small cell lung cancer to decide whether this study should continue as a phase III trial. A response was seen in 26% (10 of 38) of the patients receiving teniposide/cisplatin and in 40% (14 of 35) of those receiving paclitaxel/cisplatin. Overall, evidence of toxicity was more severe in the cisplatin/teniposide group, especially with regard to myelotoxicity. Grade 4 neutropenia was seen in 66% of patients receiving teniposide compared with 29% of those treated with paclitaxel/cisplatin. The study is to continue as a phase III trial, with 150 patients expected to participate in each treatment group.