Following reports on a variety of interactions between glutathione (GSH) concentration and clinical parameters in solid tumors, a study was undertaken in order to determine the GSH intracellular content of chronic lymphocytic leukemia (CLL) lymphocytes. The results from a group of 16 patients consecutively studied indicate tht B-CLL cells have twice as much GSH as lymphocytes from normal subjects, suggesting that this measurement may be helpful in the understanding of the metabolic mechanism of the disease and the rationale of therapy.