Retinoids influence the proliferation and differentiation of epithelial tissues. Preliminary results of a double-blind randomized trial in the prevention of recurrent superficial bladder tumors are promising. Patients treated with an oral etretinate tend to have less tumor recurrences and transurethral resections. The number of multifocal recurrences after 12 months of treatment is significantly lower (p less than 0.02). There also are less dropouts owing to inefficacy of treatment (p less than 0.036).