PURPOSE: Chemoradiation based on cisplatin, most commonly weekly, is the standard treatment of locally advanced cervical cancer; however, the nephrotoxic potential and the requirement for hydration of cisplatin somewhat restrains its use. The objective of this study was to determine the recommended dose of carboplatin when administered weekly during pelvic radiation (RT). METHODS AND MATERIALS: Twenty-four histologically proven, International Federation of Gynecology and Obstetrics Stage IIIB patients were treated with standard pelvic RT concurrently with six weekly applications of carboplatin at the following dose levels: 100 mg/m(2), 116 mg/m(2), 133 mg/m(2), and 150 mg/m(2). Six patients per level were treated. Acute toxicity was assessed according to the Radiation Therapy Oncology Group Acute Radiation Morbidity Scoring Criteria. The recommended dose was defined as the one that was one level below the level at which dose-limiting toxicity was present in more than one-third of patients. RESULTS: Between September 2001 and July 2002, 24 patients were accrued. All but two completed external beam radiotherapy and intracavitary treatment. The treatment was well tolerated. The median number of weekly applications of carboplatin was six, and the mean dose to points A and B was 85.6 Gy (range 75.2-91.6) and 62.9 Gy (range 58.2-74.6), respectively. RT was delivered within 41.7 days (range 33-70). Dose-limiting toxicity (leukopenia and/or neutropenia) was present in 50% of patients treated at the higher dose level (150 mg/m(2)). At the recommended dose of 133 mg/m(2), 33% of patients presented with Grade 3 leukopenia. At treatment completion, 75% of patients had a complete clinical response. CONCLUSION: Carboplatin at 133 mg/m(2), weekly for 6 weeks, is a well tolerated and effective radiosensitizer in cervical cancer patients.