Although advances in treatment and diagnosis have transformed HIV into a chronic disease in high-income countries, a spectrum of structural, political, sociocultural, and health system barriers hamper early diagnosis and timely treatment of HIV in many middle- and low-income countries. In most Latin American countries, in spite of the great improvement in access to antiretroviral therapy, a large proportion of individuals infected with HIV do not know their status. In Colombia, the Joint United Nations Programme on HIV/AIDS currently estimates a much larger number of HIV cases than the number reported by Colombian authorities. Potential reasons for underdiagnosis and underreporting include sociocultural factors such as social stigma, restrictions in access to health care, a lack of public health research and robust surveillance systems, and the particular recent history and social situation related to the armed conflict the country has suffered through for several decades. Lessons from Colombia may be helpful in monitoring, understanding, and tackling the HIV epidemic in countries with long-term armed conflicts.