A dormant reservoir of human immuno-deficiency virus (HIV) is established early on during primary infection which consists of latently infected, resting CD4⁺ T cells carrying replication-competent HIV. This pool can persist even in individuals who are receiving highly active antiretroviral therapy (HAART)^,,. Here we show that this pool rapidly re-emerges within weeks of discontinuing HAART in two patients, and that this re-emergence is associated with the appearance of HIV in the plasma (viraemia) of these patients. Both had been aviraemic while receiving HAART and intermittent treatment with interleukin-2 , and repeated attempts to isolate replication-competent HIV in this population of cells during therapy had been unsuccessful. This finding raises the possibility that there may be other tissue reservoirs of HIV that contribute to early plasma viral rebound following discontinuation of HAART in infected patients.