 Genetic polymorphisms of cytochrome P450 2B6 CYP2B6 are associated with lower rate of EFV metabolism and lead to high exposure, as well as a higher risk of neuropsychiatric adverse event especially homozygous variant CYP2B6 66. This trial was designed to compare the proportion of patients who had undetectable HIV RNA at 24 weeks after ART initiation between patient who did CYP 2B6 guided EFV dose and who did not. 