The Strategic Timing of Antiretroviral Treatment (START) trial began in March 2009. At that time the WHO recommendation was to start ART only when patients’ CD4 counts had dropped below 200 cells/mcL. This study involving 4685 HIV-infected people has now ended early because results showed that immediate treatment can cut the risk of disease and death in half. START included treatment-naive patients with CD4 counts >500 cells/mcL and randomly assigned half the patients to start treatment immediately, while the other half were offered ART when their CD4 count fell to 350 or they developed an AIDS-defining illness. The trial was planned to end in December 2016. However, the data safety and monitoring board found that after an average of 3 years, the early treatment group had a 53% reduction in risk of suffering an event. No evidence of undue adverse events was seen. All of the patients are now being offered treatment, with the trial continuing to follow them through 2016. The data is now likely to affect WHO and UK HIV treatment guidelines.