Taxol in phase I studies demonstrated some activity against a variety of solid tumors. The drug has undergone evaluation in phase II studies. The results of the three phase II studies of Taxol in the treatment of lung cancer that have been completed are reviewed. In the studies, the Taxol dose was 200-250 mg/m2 given intravenously over 24 hours administered every 3 weeks. All patients studied received no prior chemotherapy. In an Eastern Cooperative Oncology Group (ECOG) study, five partial responses (21%) were observed in 24 evaluable non-small-cell lung cancer (NSCLC) patients, and in the M. D. Anderson Cancer Center Trial, there was one complete response (4%) and five partial responses (20%) in 25 evaluable patients. Thirty-two evaluable patients with extensive-stage small-cell lung cancer (SCLC) received a maximum of four doses of Taxol in a study conducted by ECOG. In this study, patients could receive salvage chemotherapy consisting of etoposide plus cisplatin. The response rate was 34%. The major toxicity in all studies was leukopenia. Taxol appears to be clinically useful in the treatment of NSCLC, but more studies are needed to determine its activity in SCLC.