Recently, a randomized study conducted by the Gynecologic Oncology Group (GOG 111) demonstrated that, given by a 24-hour infusion, the combination of cisplatin and paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is superior to combination cisplatin/cyclophosphamide in previously untreated patients with advanced ovarian cancer. This combination, however, necessitates hospitalization. Combination paclitaxel/carboplatin would be expected to induce fewer nonhematologic side effects but may be more myelotoxic. Thus, we started a phase I dose-escalation study to determine the maximal tolerated dose of paclitaxel given as a 3-hour infusion in combination with carboplatin, both drugs administered every 21 days. The paclitaxel dose was escalated by increments of 25 mg/m2, starting at 135 mg/m2 (level 1), 160 mg/m2 (level 2), 185 mg/m2 (level 3), and 210 mg/m2 (level 4). Carboplatin was administered to achieve an area under the concentration-time curve of 5, using the Calvert formula For study levels 5 and 6, the carboplatin dose was targeted at area under the concentration-time curves of 6 and 7.5, respectively, and was combined with a fixed paclitaxel dose of 185 mg/m2. Thirty previously untreated patients with stage IIC to IV ovarian cancer were enrolled. Nonhematologic toxicity, including nausea/vomiting and arthralgia/myalgia, was mild. Across all dose levels, a total of 16 patients developed peripheral neurotoxicity (World Health Organization grades 1 and 2). At dose level 5, one patient experienced reversible grade 4 neurotoxicity. Neutropenia was the principal dose-limiting hematologic toxicity. During 33 (31%) of 106 courses, World Health Organization grade 4 neutropenia was observed. Granulocyte colony-stimulating factor was required in only 7.6% of courses. Thrombocytopenia was less than that expected when carboplatin is given alone. Clinical responses were observed in eight of 14 patients, for an overall response rate of 57%. The combination of carboplatin plus paclitaxel was found to be an active regimen. This trial demonstrates that carboplatin dosed by the Calvert equation and 3-hour paclitaxel can be combined safely at full therapeutic doses for six or more courses in patients with advanced epithelial ovarian cancer.