Subepidermal autoimmune bullous dermatoses are defined by clinical, histological and immunological criteria, notably the presence of anti-basement membrane antibodies detectable in vivo by direct immunofluorescence. We report three cases where anti-basement membrane antibodies were not detectable in vivo by direct immunofluorescence but were detected in high titres by indirect immunofluorescence. This situation is extremely rare in the literature. The first case concerns a 69-year old woman seen for bullous and pruriginous lesions of the lower limbs of 2 months' duration. Histological examination found dermoepidermal bullae with, in their lumen, a serous fluid spotted with numerous polymorphonuclears. A search for anti-basement membrane antibodies was positive in significant titres (1,280; 320; 480) at indirect immunofluorescence on rabbit lip whereas five successive direct immunofluorescence test in perilesional skin and on the thigh medial surface remained negative. The second case is that of a 91-year old woman suffering from generalized pruritus associated with erythematous lesions predominant on the extension surfaces of the forearms and thighs, without any bullous lesion. Pathological examination only showed a superficial dermal lymphocytic infiltrate. Four direct immunofluorescence tests were negative, whereas a search for anti-basement membrane antibodies on rat oesophagus was positive at 1/1,280. The third case resembles the second one. It concerns a 72-year old woman who consulted for generalized pruritus of several months' duration which interfered with sleep and was incompletely relieved by emollients. There was no specific skin lesion. Pathological examination revealed nothing more than a discrete perivascular mononucleate infiltrate. Direct immunofluorescence tests performed on two occasions on the skin of the abdomen and of the medial thigh surface were negative.(ABSTRACT TRUNCATED AT 250 WORDS)