To determine the significance of circulating immune complexes in dermatitis herpetiformis, serum samples from thirty patients with active disease were tested by a C1q binding radioassay, while serum samples from twenty-one of these patients were tested by a monoclonal rheumatoid factor (mRF) inhibition radioassay. By direct immunofluorescence, all patients demonstrated typical IgA deposition in dermal papillae. Using the C1q binding assay, only seven of forty-two serum samples had elevated C1q binding activity, while by the mRF inhibition assay, thirteen of twenty-five samples had elevated immune complex levels. Nine of these latter thirteen positive serum samples, however, were minimally elevated. Thus, IgG and/or IgM containing immune complexes are infrequently present, or at very low levels, in sera of patients with active dermatitis herpetiformis.