Using the Affymetrix HuGeneFL GeneChip, the global expression patterns of genes in the peripheral blood mononuclear cells (PBMCs) of rhesus macaques, infected with SIVmac251 and exhibiting rapid, typical, or slow rates of disease progression, were examined. Assessments of the change in gene expression (fold change), the temporal coordination of gene expression (self-organizing map analysis), and the similarities and significant differences in gene expression across the groups were performed on samples taken before infection and 3 and 7 weeks postinfection. An upregulation of the p27 interferon-inducible gene and of genes associated with cellular activation and immune response was observed in all three groups. Rapidly progressing animals exhibited a modest number of genes with a change in expression of 3-fold or greater, typically progressing animals exhibited the greatest number, and slowly progressing animals exhibited the fewest. Self-organizing map cluster analysis indicated that rapidly progressing animals exhibited the least coordinated gene expression over the three study time points, typically progressing animals exhibited a moderate degree, and animals with slow progression exhibited the most coordinated gene expression. Mann-Whitney U analysis indicated that differences in gene expression were most pronounced between the rapidly and slowly progressing groups and least pronounced between the rapidly and typically progressing animals. These observations elucidate distinct features of gene expression in animals with different rates of disease progression.