ObjectivesTo describe the viral response to HAART by weeks 4 and 8 in previously antiretroviral-naive patients. To assess whether the weeks 4 or 8 viral loads are useful predictors of viral suppression by week 24.DesignA large clinical database including 453 antiretroviral-naive patients whose plasma viral load was monitored every 4 weeks.MethodsObserved probabilities of achieving a viral load ⩽ 500 copies/ml by week 24 (days 84–168) from starting highly active antiretroviral therapy (HAART) were calculated according to viral loads at weeks 4 and 8.ResultsA total of 42.4% of patients (153/361) reached ⩽ 500 copies/ml viral load by week 4 and 70.4% (245/348) by week 8. Viral suppression below 500 copies/ml by 4–8 weeks was similar irrespective of the pre-HAART viral load. In patients with viral loads above 10 000 copies/ml at week 4, 60.6% (20/33) achieved ⩽ 500 copies/ml by week 24. In patients with viral loads still above 10 000 copies/ml at week 8, only 42.3% (11/26) achieved ⩽ 500 copies/ml by week 24, and only 33.3% (3/9) maintained viral suppression below 500 copies/ml to week 48.ConclusionViral loads at weeks 4 and 8 should be monitored to detect early signs of low subsequent viral suppression. For previously antiretroviral-naive patients whose viral loads after 8 weeks of HAART are still above 10 000, there is an urgent need to assess adherence to therapy, drug levels and resistance, so management can be modified accordingly to reduce the rate of week 24 virological failure.