A patient with subcorneal pustular dermatosis was found to have a circulating monoclonal IgA kappa immunoglobulin. Direct immunofluorescence studies revealed IgA kappa deposits in the subcorneal zone of the epidermis. Circulating IgA kappa reacting with the subcorneal zone of normal human epidermis was demonstrated by indirect immunofluoresence. It is speculated that IgA deposition might be implicated in the pathogenesis of subcorneal pustular dermatosis.