The Systemic Lupus Activity Measure (SLAM) is a system proposed by rheumatologists to measure disease activity in their patients with systemic lupus erythematosus (LE). It involves scoring a group of clinical symptoms and laboratory findings, the maximum possible score being 84. In systemic LE, the mid-point is between 9 and 12. We applied SLAM to 176 patients with cutaneous LE. Ninety-seven had localized discoid LE (L-DLE), 59 had disseminated discoid LE (D-DLE) and 20 had subacute cutaneous LE (SCLE). Eighty-five patients had low activity disease (0-4 points), 72 mildly active disease (5-9 points), 15 moderately active disease (10-14 points) and only four had very active disease (>/= 15 points). The most frequent lesions in patients who scored more than 10 points were photosensitivity, cicatricial alopecia, Raynaud's phenomenon and oral ulcers. Fifty patients were followed up for more than 5 years (mean follow-up 9 years). Nine of these had an increased SLAM score. Seven had L-DLE, one D-DLE and one SCLE. Seven of the 50 patients had photosensitivity, five cicatricial alopecia, five non-cicatricial alopecia, two Raynaud's phenomenon and two oral ulcers. Three patients who started with L-DLE evolved to D-DLE. The SLAM system is useful in the monitoring of disease activity in patients with cutaneous LE. Over time, even L-DLE patients may develop active disease. Photosensitivity, alopecia, oral ulcers and Raynaud's phenomenon seem to herald a worse prognosis.