Background:Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and potentially fatal disease. Little is known about the economic burden associated with CTEPH patients in the US. Abstract: Objectives:Objectives: The objective of this study was to estimate excess direct costs associated with privately insured patients with CTEPH in the US. Abstract: Methods:Methods: From a privately insured claims database (>8 million beneficiaries, 2002-7), 289 CTEPH patients were identified using the criteria: two or more claims for pulmonary hypertension (PH), International Classification of Diseases, ninth edition, clinical modification (ICD-9-CM) code 416.0 or 416.8; one or more claim for pulmonary embolism (ICD-9-CM: 415.1, V12.51; ICD-9 procedure: 38.7; Current Procedural Terminology [CPT]-4 code: 36010, 37620, 75825, 75940; Healthcare Common Procedure Coding System [HCPCS] code: C1880) within 12 months prior or 1 month after the initial PH claim (index date); one or more claim for right heart catheterization (RHC) within 6 months prior to any PH claim or one or more claim for echocardiogram within 6 months prior to a specialist-diagnosed PH claim; aged 18-64 years. Patients with CTEPH were matched demographically to controls without PH. Patients were followed as long as continuously eligible; mean follow-up in CTEPH patients was 21.5 months. Chi-squared tests were used to compare baseline co-morbidities. Wilcoxon rank-sum tests were used to compare direct (medical and pharmaceutical) patient-month costs to insurers. Abstract: Results:Results: The average age for CTEPH patients was 52.2 years, and 57.1% were women. Compared with controls, CTEPH patients had significantly higher baseline rates of co-morbidities (e.g. essential hypertension, congestive heart failure and chronic pulmonary disease) and a higher mean Charlson Co-morbidity Index score. Mean direct patient-month costs (year 2007 values) were $US4782 for CTEPH patients and $US511 for controls (p < 0.0001). Sensitivity analysis restricting the sample to patients diagnosed following RHC yielded a 15% increase in excess costs relative to the original sample. Regarding cost drivers, inpatient services accounted for 54%, outpatient and other services for 33% and prescription drugs for 11% of total direct healthcare costs per patient-month in CTEPH patients. Circulatory-/respiratory-related patient-month costs were $US2496 among CTEPH patients and $US128 among controls (p < 0.0001). Abstract: Conclusions:Conclusions: CTEPH patients had substantially higher costs and co-morbidity than matched controls, with circulatory-/respiratory-related costs accounting for 55% of excess costs. The high burden of illness suggests opportunities for savings from improved management.