This phase I study was designed to determine the maximum tolerated dose of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) with standard doses of cisplatin and etoposide for patients with untreated, extensive-stage small cell lung cancer. Secondary objectives were to determine the toxicities, response rate, response duration, and overall survival in this cohort. Twenty-four patients were enrolled into four dose levels. All patients received a fixed dose of cisplatin at 80 mg/m2 intravenously (IV) on day 1. The first group received etoposide 50 mg/m2 IV on day 1 and 100 mg orally on days 2 and 3, while all subsequent groups received etoposide 80 mg/m2 IV on day 1 and 160 mg/m2 orally on days 2 and 3. The paclitaxel starting dose was 135 mg/m2 IV over 3 hours and escalated to 175 mg/m2 and 200 mg/m2. Cycles were repeated every 21 days for a maximum of six cycles. Granulocyte colony-stimulating factor was not given prophylactically, but was allowed in subsequent cycles according to American Society of Clinical Oncology guidelines. Nineteen patients were evaluable for toxicity and 18 patients were evaluable for response. Myelosuppression was the major toxicity, with grade 4 neutropenia occurring in 18 of 19 patients (95%), but febrile neutropenia was uncommon and developed in four of 19 patients (21%). Dose-limiting peripheral neuropathy was observed at a paclitaxel dose of 200 mg/m2. Grade 4 nausea/vomiting and diarrhea were also noted at this dose level. Four patients had complete responses (22%) and 13 patients had partial responses (72%). The overall response rate was 94%, with a median survival of 11 months and a 2-year survival rate of 19%. This three-drug combination of paclitaxel with cisplatin and etoposide is highly active with acceptable toxicity. Neurotoxicity was dose limiting at 200 mg/m2 paclitaxel. Neutropenia was frequent but was not associated with significant morbidity. The recommended doses for future clinical trials are paclitaxel 175 mg/m2 IV over 3 hours on day 1 with cisplatin 80 mg/m2 IV on day 1 and etoposide 80/160 mg/m2 IV on day 1 and orally on days 2 and 3. Growth factor support should be used according to American Society of Clinical Oncology guidelines.