Thirty-two patients with locally advanced head and neck cancer have been treated with concurrent weekly carboplatin and conventional radiation therapy (RT) (2 Gy fractions 4-5 days/week to a total dose of 64-70 Gy over 7-8 weeks) in a Phase I/II study. Carboplatin was administered weekly during RT at doses of 75-150 mg/m2/wk as a 1-hour infusion. The maximum tolerated dose of carboplatin was 130 mg/m2/wk, with myelosuppression, predominantly neutropenia, being dose limiting. Other systemic toxicities were insignificant and no overlapping toxicity was evident. Ultimate locoregional control and survival probabilities were disappointing. It is suggested that either further studies using radiation and carboplatin at the dose 130 mg/m2/wk, or variations on dose and scheduling be performed prior to the instigation of Phase III studies.