New Zealand Black/New Zealand White (NZB/W) mice, a model of systemic lupus erythematosus (SLE), have age-dependent loss of interleukin-2 (IL-2) production. To determine if replacement therapy would influence the course of autoimmune disease, we injected groups of NZB/W mice with low-dose (1,500 units/day) or high-dose (15,000 units/day) purified human recombinant IL-2. Parameters of active SLE and populations of splenocytes were not altered consistently by long-term treatment with either dose of IL-2.