The United Nations is committed to achieving universal access to human immunodeficiency virus (HIV) care, treatment, and prevention. Although the gateway to HIV care and secondary prevention is knowledge of serostatus, use of voluntary counseling and testing in resource-limited settings with the highest burden of HIV infection and AIDS has been limited. On the basis of evidence of increased patient uptake and the opportunity to avoid missed HIV testing opportunities in health care facilities, in 2007, the World Health Organization recommended provider-initiated HIV testing as a standard part of medical care in settings with generalized HIV epidemics. Although provider-initiated testing has shown promise, optimal implementation strategies that ensure broad coverage, while preserving human rights, remain an active area of research. We review the benefits of knowledge of HIV serostatus and evidence from multiple countries surrounding the successes and pitfalls of provider-initiated testing in health care and home-based settings.