Ten patients suffering from either discoid lupus erythematosus (DLE) or subacute cutaneous lupus erythematosus (SCLE) were treated with interferon alpha 2a. Eight received low or intermediate doses (18-45 x 10(6) U/week) for a short period of time (4-8 weeks), with marked improvement of skin lesions in six, an exacerbation in one patient and no change in the other. Two patients with SCLE received high doses (100-120 x 10(6) U/week) over 12 weeks, with complete clearing of the lesions in one and a marked improvement in the other. The responses were of short duration and within a few weeks of stopping treatment all who had improved or cleared relapsed. The side-effects in all the patients were fever and a flu-like syndrome which necessitated a reduction of the dose in one case. In two patients there were increases in the liver enzyme levels, but no haematological toxicity was noted.