OBJECTIVES: Treprostinil is available in two forms (inhaled vs. infused) for the treatment of patients with pulmonary arterial hypertension (PAH) and New York Heart Association (NYHA) Class II-IV symptoms. The preference from 384 members of the general public for the inhaled form, and this population’s willingness-to-pay (WTP) in additional monthly insurance premiums for the inclusion of this treatment on a hypothetical insurance scheme have been previously reported.  The present cost-benefit analysis (CBA) explored whether it would be cost-beneficial to include inhaled treprostinil to a list of medications reimbursed by private third-party payers in Canada, for PAH NYHA Class III patients. METHODS: The CBA was based on a hypothetical population of 100,000.  Total yearly benefits were calculated by targeting subjects 18 years of age or older and active in the workforce, applying the percentage of subjects who prefer inhaled treprostinil to infused treprostinil (85.8%) and their median monthly WTP ($CAD21.50) multiplied by 12.  Potential costs were evaluated by estimating the number of potential PAH patients in the hypothetical cohort, 18 years of age or older and in NYHA Class III category, multiplied by the annual cost of using inhaled treprostinil ($117,893).  The final cost-benefit to third-party payers was appraised by subtracting the potential costs from the potential benefits. RESULTS: Based on prevalence rates, the hypothetical starting cohort would yield 2 patients, resulting in expected costs of $235,786 to third-party payers.  The estimated number of subjects willing to pay for the inclusion of inhaled treprostinil on the formulary of reimbursed drugs was 37,540, generating benefits of $9,685,320.  Hence, the expected difference (benefits minus costs) was $9,449,534. CONCLUSIONS: The inclusion of inhaled treprostinil to formularies of reimbursed medications would be highly cost-beneficial to private third-party payers in the province of Ontario, Canada, for patients with PAH and NYHA Class III symptoms.