The time course of the change in antibody titres was examined postpartum after treatment in two patients with herpes gestationis. The first patient, a 29-year-old woman seen first in the 32nd week of her first pregnancy, had an exudative erythema, and developed an itchy erythema with small tense vesicles on the trunk and legs after delivery in the 40th week of pregnancy. The second patient, a 28-year-old woman seen first in the 28th week of her first pregnancy, had an itchy exudative erythema, small tense vesicles and crusts on the legs. After a Caesarean section in the 40th week of pregnancy performed because of cardiac complications in the fetus, the skin lesions extended to the trunk and extremities. Direct immunofluorescence revealed linear depositions of IgG and C3 at the basement membrane zone (BMZ) and indirect immunofluorescence was positive at the epidermal side of the BMZ in 1 mol/L NaCl-split skin in both cases. In patient 1, prednisolone, 20 mg/day, administered 4 months after delivery, gave rapid improvement (within 1 week) of the skin lesions; in patient 2, minocycline, 200 mg/day, administered 2 weeks after delivery, gave improvement within 2 weeks. Immunoblotting against epidermal extracts revealed the presence of antibodies directed to the 180 kDa bullous pemphigoid antigen in both sera. Indirect immunofluorescence and immunoblot were positive for at least 2 months in patient 1 and for 5 months in patient 2 after disappearance of the skin lesions.