Quantification of CD4+ T lymphocytes and viral RNA in patients with HIV/AIDS. Levels of progression markers (viral load and CD4+ T lymphocytes) in 410 patients with HIV/AIDS that were in different clinical stages of the disease and under different therapeutic schemes were quantified. The objective was to determine the correlation between values of progression markers and clinical stage of the patients. Commercial methodologies for the quantification of lymphocytes, subpopulations and circulating viral RNA were used. Results indicate that there was a correlation between low CD4+ values and high viral load in patients with antiretroviral treatment but not in patients without treatment. Furthermore, analysis of 1,208 samples processed during 1999 showed that 46% of the patients had less than 200 CD4+ T lymphocytes/mL blood and more than 500 copies of circulating viral RNA. Implications of these results in public health in Mexico are discussed.