We studied the autoimmune serologic features and histocompatibility antigen associations of 27 patients who had a widespread, nonscarring and often photosensitive form of histologically specific cutaneous lupus erythematosus. We designated this disorder as subacute cutaneous lupus erythematosus. Skin lesions from this disorder can be distinguished from scarring discoid lupus erythematosus lesions both on a morphologic and histopathologic basis. Antinuclear and anticytoplasmic antibodies (Ro or Ro and La) and circulating immune complexes were frequently present in patients with subacute cutaneous lupus erythematosus, whereas rheumatoid factor and anti-lymphocyte, anti-DNA, anti-nRNP, and anti-Sm antibodies were found less frequently. Patients having annular skin lesions represented a particularly homogeneous subgroup in which there was a striking concordance of anti-Ro antibodies and the HLA-DR3 phenotype. These studies clearly establish that the presence of these lesions can serve as a cutaneous marker for a distinct subset of patients with lupus erythematosus who share similar clinical, serologic, and genetic features.