This phase I trial was designed to determine the maximum tolerated dose of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) given as a 3-hour infusion in combination with carboplatin (400 mg/m2) as first-line chemotherapy for stage IIIC/IV ovarian adenocarcinoma. After premedication, paclitaxel was infused over 3 hours, followed by carboplatin infused over 30 minutes on day 1 of a 28-day cycle (group 1, with 28 patients accrued and 150 evaluable cycles) or on day 1 of a 21-day cycle (group 2, with 16 patients accrued and 55 evaluable cycles). Dose-limiting toxicities assessed after the first course included grade 4 neutropenia lasting longer than 7 days, febrile grade 4 neutropenia requiring intravenous antibiotics, grade 4 thrombocytopenia, mucositis greater than grade 2 for more than 7 days, grade > or = 3 nonhematologic toxicity (excluding alopecia, vomiting, and muscular pain), no hematologic recovery on day 42 (for group 1) or on day 35 (for group 2), neurotoxicity above grade 2, and persistence of nonhematologic toxicity (excluding alopecia, nausea/vomiting, and musculoskeletal pain) grade > or = 2 at scheduled re-treatment. If any of the events occurred during the first cycle in three or more of six patients, maximum tolerated dose was considered to have been reached. The hematologic toxicity associated with the two treatment schedules was mainly neutropenia, but it was of short duration. Very few dose reductions or dose delays were necessary. Until now, the six planned courses have been administered without colony-stimulating factors. No toxic death has occurred. Grade 2 or 3 peripheral neuropathy has occurred in 12% of patients, mainly with high doses of paclitaxel. At this time, the maximum tolerated dose has not been reached at paclitaxel 275 mg/m2 every 4 weeks or 225 mg/m2 every 3 weeks, and enrollment continues.