OBJECTIVES: The present study determined the total direct health-care costs for the management of PAH patients with differing degrees of disease severity. The study also aimed to find the key cost drivers in the management of PAH. METHODS: PAH patients were recruited from a tertiary care hospital between January 1, 2009 and 2011. One-year costs were identified by applying cost data to medical information obtained by review of medical records. Costs included those for medications, laboratory and diagnostic tests, clinic visits, emergency room visits and hospital stays. Contemporary data were obtained from epidemiological studies, government datasets, and other sources to estimate prevalence. National costs (US dollar 2012) of treatment for PAH were estimated by extrapolation of mean cost estimate per person to national incidence data for PAH. Because of uncertainties surrounding some of our estimates such as prevalence, one way sensitivity analyses were undertaken. RESULTS: A total of 113 PAH patients were identified and their demographic and clinical characteristics, patterns of care were examined. The mean age was 38 years, and 83% were female. The average per patient annual cost was $ 10,869 without specific treatment (min $ 137; max $155,928). The annual cost for the treatment of a single PAH patient per year with specific therapy (Bosentan) was calculated in $31.433. Aggregate national health care expenditures for treatment of PAH were USD 46.6 million In multivariate analysis, length of hospital stay, stay in ICU, were all significant independent predictors of treatment CONCLUSIONS: There is a correlation between the cost of HAP and disease severity with hospitalization owing to disease severity being a major contributor to cost. With the expected increase in the incidence of PAH in Mexico over the coming decades, these results emphasize the need for effective preventive and acute medical care.