A phase I study of 13-cis-retinoic acid was done in 16 patients with head and neck malignancies using a modified Fibonacci search scheme, with individual doses ranging from 20 to 120 mg/m2. Drug doses greater than 60 mg/m2 induced intense headaches, urethritis, desquamative dermatitis, vertigo, and ataxia. The severity of these side effects precludes the use of 13-cis-retinoic acid as a potential chemopreventive agent at doses greater than 60 mg/m2.