Patients with squamous cell carcinoma of the head and neck (HNSCC) after being treated radically remain at high risk for both recurrent and second primary tumours. 13-cis retinoic acid (13-cRA) was demonstrated to reverse pre-malignant lesions of the oral cavity and to reduce the incidence of second primary tumours in patients treated radically for HNSCC. Synergism between retinoids and interferon in tumoural cell lines have been demonstrated. Based on these data, the Italian Head and Neck Chemoprevention Study Group started a randomized chemoprevention study in patients radically treated for stage III and IV HNSCC. From February 1992 to January 1996, 267 patients were randomized: 126 were allocated to the control group, 126 were randomized to receive 13-cRA at a dose of 0.5 mg/kg per day per os and 15 patients have been assigned to the group of 13-cRA plus interferon alpha2a (IFN-alpha2a) at a dose of 3,000,000 UI 3 times a week (randomization in this arm interrupted due to administrative financial problems). The mean follow-up was 39 months. The 5-year actuarial survival was 58.9% for patients of the 13-cRA group and 57.2% for those of the control group (P=0.94). Among evaluable patients, disease progression was observed in 45 of 123 patients (36.6%) of the 13-cRA group and in 42 of 124 (33.9%) of the control group. The 5-year actuarial relapse-free survival was 48.9% for the 13-cRA group and 55.6% for the control group (P=0.62). Adverse effects, mostly of grade I were reported in 69.4% of treated patients (haematologic disorders, mucositis, conjunctivitis, cutaneous toxicity, hypertriglyceridemia and hypercholesterolemia). Only 5 patients (4.1%) reported grade III-IV toxicity. Low-dose of 13-cRA given for 1 year is ineffective as chemoprevention in patients with radically treated HNSCC.