The influence of a 2-h neuropsychological stress test on plasma catecholamines, cortisol, and on the distribution of lymphocyte subpopulations was studied in 14 patients with systemic lupus erythematosus (SLE), 10 patients on prednisone treatment (without collagenosis), and 14 sex-and-age-matched healthy controls. Psychological stress induced comparably significant increases in plasma adrenaline and noradrenaline levels as compared with baseline values (P less than 0.05) in all three groups, whereas plasma cortisol remained unchanged. The rise in plasma catecholamines was accompanied by a significant cell mobilization in healthy subjects and prednisone-treated patients, but not in patients with SLE. CD19+ cells increased significantly in number from baseline in healthy subjects and prednisone-treated controls (P less than 0.05), while remaining unchanged in SLE patients. In conclusion, SLE patients showed a reduced cell mobilization due to psychological stress despite hormonal alterations paralleling those of healthy subjects or prednisone-treated patients without collagenosis.