Human leukocyte antigen (HLA)-B*5701 allele is associated with abacavir hypersensitivity. Limited data among Asians showed lower rates of HLA-B*5701 compared with Caucasians. In 296 children with HIV in Thailand and Cambodia, the prevalence of HLA-B*5701 was 4.0% (95% confidence interval: 1.6-8.0%) among Thai and 3.4% (95% confidence interval: 0.9-8.5%) among Cambodian children. HLA-B*5701 carriage is not uncommon among Thai and Cambodian children; it is close to the prevalence found in European and higher than the prevalence found in East Asian and African studies.