Interest in regulatory T cells (Treg) has been continuously growing over the last 10years. In particular, a role for Treg has been recently reported in HIV. It is crucial to investigate their conservation over time, once sampled and purified. The objective of the present study was to investigate whether cryopreservation may modify recognition and measurement of relative frequency of Treg (CD4(+)CD25(+)CD127(-)) among PBMCs purified from 17 HIV-infected patients. Ours results indicate that cryopreservation does not affect this specific T lymphocyte subset.