It has been suggested that patients with homogeneous linear IgA deposits at the basement membrane zone constitute a distinct bullous disorder called linear IgA dermatosis (LAD) of adults or children. The results of the present ultrastructural immunogold study in two patients with LAD suggest that LAD is not a single disease entity. LAD in a 10-year-old girl was found to be ultrastructurally similar to an IgA-type pemphigoid. IgA was detected in the uppermost lamina lucida underlying the basal cell plasma membrane. In a second patient, an 86-year-old man, IgA deposits were present within the lamina densa and the anchoring plaques. The distribution of IgA in this patient was ultrastructurally identical with that of IgG in epidermolysis bullosa acquisita skin and with that of the non-collagenous globular terminus of collagen VII within the basement membrane zone of normal skin. By using the immunogold technique, we could distinguish two distinct types of LAD according to the IgA binding sites in the diseased skin. We suggest that different labelling patterns may correspond to different clinical pictures.