To study the effect of age on several outcomes among 187 antiretroviral-naive infected patients who started highly active antiretroviral therapy (HAART) with <or=200 CD4(+)/microl. We carried out a retrospective study to determine the hazard ratio (HR) to reach an outcome in patients who experienced a change from the baseline in CD4(+) counts of at least +100, +200, +300, +400 and +500 cells/microl at any moment during the follow-up and the odds ratio (OR) of achieving and maintaining a CD4(+) value above a certain setpoint during at least 6, 12 or 18 months. The adjusted HR for an increase of +400 CD4(+)/microl and +500 CD4(+)/microl were 1.3 (95% CI: 1.1; 1.5) and 1.3 (95% CI: 1.1; 1.6) times slower for each additional 5 years of age at baseline. In addition, for every 5 years of extra age, the adjusted OR to achieve an absolute CD4(+) cell count >500/microl at 6, 12 and 18 months after the initiation of HAART were 2.2 (95% CI: 1.5; 3.2), 1.8 (95% CI: 1.2; 2.6), and 1.8 (95% CI: 1.2; 2.9) times less likely, respectively. We also found that patients >or=45 years old had worse complete CD4(+) recovery (CD4(+)>500 cells/microl) than patients <45 years old. The CD4(+) recovery after HAART is a prolonged and continuous process which extends for several years. Age at baseline is inversely correlated with the magnitude and speed of CD4(+) recovery among HIV-1 infected patients.