We collected human immunodeficiency virus (HIV) disease progression, survival, most recent CD4 cell count, and plasma HIV RNA levels from patients (n = 157) who participated in randomized clinical trials of interleukin (IL)–2 that commenced before 1995. Data were available for 155 (99%) patients. Statistical analyses were based on the intention-to-treat principle. Median follow-up was 28 months and 30 months for control and IL-2 patients, respectively. Twenty-five (16%) patients developed AIDS or died during follow-up (16 control patients vs. 9 IL-2 patients; R² = 0.57; P = .22). Mean change from baseline CD4 cell count was significantly higher in patients randomized to receive IL-2 (368 vs. 153 cells/µL; P = .003). Mean change from baseline plasma HIV RNA was significantly lower in patients randomized to receive IL-2 (−0.98 vs. −0.63 log copies/mL; P = .004). Significant improvements in CD4 cell count and plasma HIV RNA in recipients of IL-2 relative to control patients were associated with a nonsignificant trend toward improved clinical outcome.