As shown in Table 1, the hazard ratio of progression to AIDS or death before April 1997 was 50.8 (p<0.01) in CD4 cell counts of less than 200 cells/μL and 7.7 (p=0.05) in those of 200-349 cells/μL compared with those of 500 cells/μL or more. Here, CD4 is linked to AIDS.