Forty-five patients suffering from various genodermatoses and erythematous, scaling, non-psoriatic dermatoses were treated orally with the aromatic derivative of retinoic acid, Ro 10-9359 (Tigason). In the genodermatoses the best results were obtained in ichthyosis, keratodermias and Darier's disease (95.6% good to excellent). Among the erythematous scaling diseases, treatment was effective in lichen planus, parapsoriasis and pityriasis rubra pilaris (53.3% good to excellent results). In comparison with therapies previously employed Ro 10-9359 was more effective. No serious side-effects were noted.