Eighteen patients with advanced squamous cell cancer of the head and neck were treated with cis-diamminedichloroplatinum in a 24-hour infusion. The most frequent dose used was 80 mg/m2 repeated every three weeks. Six were treated preoperatively for Stage III or IV disease, and twelve were treated for recurrent disease. The overall response rate was 72% with one complete remission, greater than 50% regression in six patients, and 25--50% regression in six patients. Toxicity was minimal: creatinine greater than 2 in 6% of courses, leukopenia in 9%, anemia in 29%, vomiting in 76%, and documented minimal hearing loss in one patient. Plasma and urine platinum levels during infusion are presented. The dosage of 80 mg/m2 administered over 24 hours gives a response rate in head and neck cancers equivalent to that reported with higher doses given by rapid infusion, and toxicity is minimal.