A prospective study was conducted with 161 human immunodeficiency virus (HIV)-positive patients to investigate the prognostic role of 10 serum-modified nucleosides with regard to some of the most widely used parameters of AIDS progression. Serum concentrations of pseudouridine (> 3.77 nmol/mL) predicted progression to AIDS in CDC stage A2 HIV-infected patients much better than did other widely used parameters (hazard ratio, 2.7; 95% confidence interval, 1.29-6.35; P = .01; median permanence time in stage A2, 17 vs. 30.5 months; P = .03). Serum concentrations of 1-ribosylpyridin-4-one-3-carboxamide (PCNR) and beta 2-microglobulin and the CD4:CD8 cell ratio, in decreasing order and used in combination, differentiated the overall survival time probability of AIDS patients; PCNR was the best and a new independent predictor (overall survival time, > 31 months, no positive parameters; 19.3 months, one positive parameter; and 5.5 months, two positive parameters.