Twenty-nine chemotherapy-naive patients with primary hepatocellular carcinoma were treated with oral beta-all trans-retinoic acid (retinoic acid, TRA 50 mg/m2 t.i.d.) on a 3-week on/one week off schedule until progression or grade 3 or 4 toxicity. Eligibility requirements allowed abnormal liver function tests as long as the creatinine and bilirubin levels were normal. No responses were seen and the median survival was four months. Grade 3 side effects occurred in II patients and grade 4 in four and included a wide range of toxicities. The results indicate that oral TRA is ineffective against primary hepatocellular carcinoma and suggest that dose-modification of this retinoid may be required in patients with significant malignant hepatic involvement.