The World Health Organization (WHO) has developed a global laboratory network to support human immunodeficiency virus drug resistance genotyping for public health surveillance in resource-limited countries. Blinded proficiency panels are an essential part of a genotyping quality-assurance program and are used to monitor the reliability of genotyping data in the WHO laboratory network. Laboratories in Europe, North America, Asia, Africa, and the Caribbean have tested panels annually since 2007; 103 of 131 submissions (79%) had >99% nucleotide sequence identity and resistance mutation concordance, compared with consensus. Most errors were associated with mixtures in the test specimen, leading to subjectivity in base-calling or amplification bias. Overall, genotyping assays used by the WHO laboratory network are reliable.