Ever having recorded a CD4 cell count < 200 cells/mm3 (before or during treatment) was strongly associated with increased hazards for AIDS (HR 3.61 CI95 2.25 – 5.82, p < 0.001) and death (HR 9.00 CI95 4.04 – 20.02, p < 0.001), while ever having recorded a CD4 cell count > 500 cells/mm3 (before or during treatment) was strongly associated with reduced hazards for AIDS (HR 0.30 CI95 0.21 -0.41, p < 0.001) and death (HR 0.08 CI95 0.04 - 0.19, p = 0.000), independent of other covariates. This evidence concerns the gene CD4 and AIDS.