Smaller CD4 gains by six months were associated with higher hazards of progression to AIDS (CD4<50 vs. ≥200 cells/ml; adjusted hazard ratio (aHR): 2.6; 95% CI: 1.2–2.1) and death (aHR: 2.8; 95% CI: 1.4–5.7). The gene discussed is CD4; the disease is AIDS.