One hundred twenty patients with acute and chronic discoid lupus erythematosus, psoriasis, and a variety of chronic skin diseases were studied for the presence of antinuclear antibodies (ANA) in their sera. Fourteen of 19, or 74% of those with active acute systemic lupus erythematosus were found to have positive ANA tests in dilutions of 1:20 up to 1:1,280, while in chronic discoid lupus erythematosus the ANA test was found to be negative in 43% and positive in dilutions of less than 1:20 in the remaining 57%. All other patients with chronic skin disorders had negative ANA tests as did the 20 control subjects. Quantitation of the fluorescent antibody test is of value in differentiating chronic discoid from acute systemic lupus erythematosus.