The objectives of this phase I/II trial were to determine the maximum tolerated dose, toxicities, and the dose suitable for phase II/III trials of irinotecan (CPT-11) combined with paclitaxel and carboplatin in patients with advanced non small-cell lung cancer (NSCLC). Seventy-three patients with stage IIIB/IV NSCLC were enrolled in this multicenter, phase I/II study. The initial regimen was paclitaxel 225 mg/m2 over 3 hours, followed by carboplatin at an area under the curve (AUC) of 6 over 30 minutes on day 1 and CPT-11 starting at 40 mg/m2 over 90 minutes on days 1 and 8, every 3 weeks. Dose-limiting toxicity occurred in three of the original seven patients. The regimen was amended with doses reduced to paclitaxel 175 mg/m2 over 3 hours, carboplatin AUC = 5, and CPT-11 at 40 mg/m2, all on day 1 every 3 weeks. Dose escalation of CPT-11 proceeded to 80 mg/m2 and 125 mg/m2 before dose-limiting toxicities were experienced. Subsequent patients received an intermediate CPT-11 dose of 100 mg/m2. Doses suitable for phase II study were determined to be paclitaxel 175 mg/m2 over 3 hours, carboplatin AUC = 5, and CPT-11 100 mg/m2. The pri-mary first-cycle dose-limiting toxicities were neutropenia and diarrhea. The most common grade 3/4 toxicity observed during all cycles was neutropenia. On the phase I portion of the study, objective tumor response was observed in 39% (12 of 31, 95% confidence interval: 22%-58%). The median time to tumor progression was 6.8 months, median survival was 11.0 months, and 1-year survival probability was 0.46. These data were confirmed in the phase II portion with a 30% objective response rate, median time to progression of 5.6 months, median survival of 12.5 months, and a 1-year survival probability of 0.50. In conclusion, CPT-11 100 mg/m2, paclitaxel 175 mg/m2, and carboplatin AUC = 5 given every 3 weeks can be safely administered in patients with advanced NSCLC. Neutropenia and diarrhea are the dose-limiting toxicities. The combination shows appreciable activity, and survival data are favorable, warranting further study of this regimen. A review of other irinotecan-containing triplet combinations is presented.