Plasmapheresis was used as the sole treatment modality in 4 patients with systemic lupus erythematosus. The presence of circulating immune complexes in this group of patients was not predictive of response to plasmapheresis. Lymphocytotoxic antibody levels fell in 3 of the 4 patients, and no consistent changes in T lymphocytes, T lymphocyte subsets, complement, or immunoglobulin levels were observed. Followup during the subsequent 6 months showed deterioration in clinical and laboratory parameters in all 4 patients, and the protocol was discontinued. Plasmapheresis without concomitant therapy may be detrimental to certain patients with systemic lupus erythematosus.Plasmapheresis has been described as valuable in the treatment of several immunologically mediated diseases ( 1-6), including systemic lupus erythematosus (SLE), in which the presence of circulating immune complexes (CIC) has been proposed to be predictive of a favorable response to plasmapheresis (5,6). However,