Highly active antiretroviral therapy (HAART) has dramatically improved the prognosis of patients with HIV, although it remains unclear as to the best time to start treatment to reduce the risk of clinical progression. The initial virological response to HAART, by reducing viral load to below the limit of detection, is essential for reducing the risk of drug resistance, which in the longer term may lead to a deterioration in immune function and an increased risk of clinical disease progression. There has been a switch to more conservative therapy recently, given concerns about toxicities and the difficulties of adhering to a complicated regimen long term.