OBJECTIVES: To conduct cost-effectiveness analysis of bosentan and sildenafil compared with standard therapy (ST, i.e. calcium channel blockers and warfarin) in treatment of primary pulmonary arterial hypertension (PAH) in Russian Federation. METHODS: We undertook cost-effectiveness analysis of bosentan (62.5 mg bid during first 4 weeks and 125 mg bid further) and sildenafil (25 mg tid) and estimated incremental cost-effectiveness ratios (ICER) for each drug vs ST. A cohort of 20 patients with PAH, functional class (FC) III was simulated in a model. The patients either received bosentan+ST, or sildenafil+ST, or ST only. The number of patients whose health state improves by one FC was considered a criterion of efficacy. Costs of hospitalization, standard therapy medications, and investigational drugs were calculated in the model. Data on clinical efficacy of bosentan, sildenafil, and ST were extracted from clinical trials. Patient’s treatment scheme considered in the model was based on the results of peer interview. RESULTS: In our model treatment with bosentan was the most effective: 9 of 20 patients versus 6 and 2 of 20 patients who had improved by one FC with bosentan, sildenafil and ST, respectively. Also, the highest overall costs were in the bosentan group: 1,163,948 USD per 20 patients per year. Overall costs in case of sildenafil and standard therapy were 724,520 and 57,969 USD per group per year, respectively. However, comparison of bosentan with ST yielded lower ICER than comparison of sildenafil with ST: 157,997 and 166,638 USD per one patient with improvement by one FC, respectively. Trend in the results remained the same with bosentan price up to 4400 USD per pack in one-way sensitivity analysis.   CONCLUSIONS: The results of this study suggest that treatment of FC III PAH with bosentan is more preferable than treatment with sildenafil.