The treatment of herpes gestationis has been considerably changed in recent years by progress in electron microscopy and immunology. Herpes gestationis, a rare polymorphic vesiculo-bullous pruriginous dermatosis, occurs during pregnancy or the post-partum period. It evolves by acute periods of several weeks, and relapses during later pregnancies or on taking oestro-progestagens. Histologically, the bulla is situated at the dermo-epidermic junction. The epidermal oedema is both intra and extra-cellular. The ultrastructural studies show the importance of the oedema and the changes in the plasma membrane of the basal cells in the onset of the vesicles and the bullae. The immunological inquiry gives diagnostic certainly when one discovers under indirect immuno-fluorescence, a specific serum factor, the herpes gestationis factor. These ultrastructural and immunological data suggest a relationship between herpes gestationis and bullous pemphigus (Lever's disease). In treatment, the possible pathogenic role of prolactin suggests the use of bromocriptin during the postpartum period. The efficacy and innocuity of vitamin B6 make corticosteroids rarely necessary.