The substituted benzamides or orthopramides are used to treat gastrointestinal and psychotic disorders. The orthopramide clebopride, a potent dopaminergic antagonist, blocks emesis in dogs and stereotyped behavior in rodents. Since the release of prolactin is inhibited by dopamine, antidopaminergic drugs may be useful to increase lactation in nursing mothers. The present work examines the morphological and histological alterations produced by long-term treatment of puerperal and virgin female rats with clebopride. Clebopride induced significant hyperplasia of parenchymal secretory units and stimulated milk secretion in both groups of rats. However, only in virgin rats was mammary weight significantly increased.