We studied the production of and response to interleukin-2 (IL-2) by peripheral blood T lymphocytes from 19 systemic lupus erythematosus (SLE) patients who received no treatment at the time they were studied. Eight had active disease and the rest were in remission. Results were compared with those obtained in 12 healthy subjects of similar age. T cells from SLE patients, whether activated with phytohemagglutinin or in autologous mixed lymphocyte reactions, were found to yield little IL-2, to have a low response to IL-2 from its own, or other sources, and to absorb IL-2 poorly, IL-2 produced by SLE cells, albeit scant, was absorbed normally by activated T cells from normal subjects. Our findings may contribute to the understanding of the immunoregulatory defect in SLE.