OBJECTIVES: HIV/AIDS prevalence in Colombia is 0,8%. Currently for the country is important to assess the effectiveness and impact of its practices on the health of its population. A health maintenance organization (HMO) with national coverage aims to contribute by assessing the health outcomes of its care program for HIV/AIDS patients, a high cost disease with great impact on HRQOL. To evaluate the cost-effectiveness of the care program for HIV/AIDS patients insured by a HMO in Colombia, comparing its results in three health care providers (HCP). METHODS: A Markov model in MS Excel® was built to represent the natural history of HIV/AIDS based on the staging of the disease given by WHO according to the CD4 lymphocytes level. Direct costs were included, according to the information available on HMO´s databases. The outcome measure were QALY's taken from the literature. Transition probabilities were calculated from tracking a cohort of 884 HIV/AIDS patients over 18 years old, from three health providers (HCP A, B and C) in 7 cities across the country, during 2011 and 2012. Time horizon was lifetime. Perspective was third payer. Deterministic and probabilistic sensitivity analysis were performed. RESULTS: HCP C was dominated. HCP A versus HCP B ICER was USD$2.497 per life year gained and USD$3.674 per QALY. Annual average cost per patient by stage was: stage 1 USD$2.347, USD$2.281 stage 2, stage 3 USD$3.022, USD$4.103 stage 4 and USD$6.994 for stage 5. CONCLUSIONS: Given a willingness to pay 1 GDP per capita for the country, the HCP B is a very cost-effective option. The average annual cost of patients in stage 5 is three times stage 1. PRIMARY FUNDING SOURCE: health maintenance organization (HMO).