This study reports comparative results of the effects of an aromatic retinoid, etretinate (RO 10-9359), on various disorders of the skin and mucous membranes. One hundred thirteen patients suffering from psoriasis, lichen planus, keratosis follicularis, and various other disorders were treated and examined. The patients received 25 to 100 mg/day of oral etretinate for up to 30 months. Patients with erythrodermic psoriasis, pustular psoriasis, and keratosis follicularis showed the best response. The conditions of patients with psoriasis vulgaris, palmoplantar psoriasis, and lichen planus also improved, but less impressively. The mucous membrane lesions of lichen planus and leukoplakia showed only moderate improvement. The most striking adverse clinical reactions observed were cheilitis (70%), dryness of the mucous membranes (27%), and hair loss (27%).