In a prospective study of 226 patients with systemic lupus erythematosus (SLE), 91 patients (40%) had Raynaud's phenomenon. These patients were compared to 135 patients without Raynaud's phenomenon. Patients with Raynaud's phenomenon had a greater incidence of arthritis (P less than 0.02), malar rash (P less than 0.003), and photosensitivity (P less than 0.03), and a lesser incidence of severe renal disease as manifested by serum creatinine over 3.0 mg/dl (P less than 0.007) or creatinine clearance below 60 ml/minute. Patients with Raynaud's phenomenon were less likely to have severe, life threatening disease and received a lower average monthly (P less than 0.01) and a lower peak daily corticosteroid dose (P less than 0.01). Fourteen patients (16%) with Raynaud's phenomenon died, compared to 41 without (30%) (P less than 0.03). Raynaud's phenomenon in patients with SLE is associated with milder disease and may be regarded as a favorable prognostic sign.