Tissue culture allows HIV to be expanded and propagated in vitro by its culture with donor peripheral blood mononuclear cells in the presence of stimulatory factors such as interleukin 2 (IL-2). Coculturing of patient peripheral blood mononuclear cells, or cells from other body compartments suspected to be infected with HIV, with stimulated donor peripheral blood mononuclear cells is an alternative method for the detection of very low levels of virus. Culture supernatants are assayed for the presence of p24 or reverse transcriptase, which generally appear over 1 to 2 weeks. The eﬃciency of the process falls dramatically with lower HIV viral load, although it can be improved by using techniques such as the removal of inhibitory CD8 cells from the patient and donor peripheral blood mononuclear cells, stimulation with phytohaemagglutinin or IL-2. The tissue culture technique is expensive and time-consuming and must be performed only within a laboratory with appropriately certiﬁed biocontainment. For viral detection and isolation in clinical situations, tissue culture has now been replaced by the methods outlined above and is never performed as a routine test. However, it remains a mainstay of laboratory practice, where it is used for the maintenance and analysis of viral strains.