HIV reservoir measurement in patients is one of the challenges at the time of testing new treatment approaches aiming at eradicating HIV infection. HIV reservoirs are complex and disseminated in a large number of organs and lymphoid tissues. We chose to quantify total cell-associated HIV-DNA in PBMC as a marker of HIV reservoirs and described the method we developed. The marker was used in large cohort studies at different stages of HIV disease and in therapeutical trials. Our results show how informative is this marker, as well as that plasma HIV-RNA and CD4 T cell count are representative of each patient when measured in blood. Such a series of results might help to adapt simplification or structured interruption strategies, design new clinical trials targeting HIV reservoirs, and select populations that could benefit of such new treatments.