Skin biopsies from 13 patients with papular lesions thought to be cutaneous lupus erythematosus were analyzed by light microscopy, direct immunofluorescence and immunohistochemically and compared to 22 biopsies from patients with discoid lupus, subacute cutaneous lupus erythematosus and acute cutaneous lesions of SLE. Papular lesions demonstrated fewer florid dermal and epidermal changes but a similar marked mononuclear cell infiltrate which in all groups was composed predominantly of T lymphocytes (68.4 +2- 11.2 SD) with the mean helper: suppressor (corrected Leu 3a:T8) ratio 1.73 +/- 0.60 SD. HLA-DR expression on keratinocytes was present in 20 patients, including 4 with papular lesions, and was strongly associated with liquefactive degeneration (chi 2, p less than 0.001), the hallmark of dermoepidermal junctional damage.