OBJECTIVES: To examine utilization of healthcare services and factor concentrate among persons with hemophilia A receiving care at U.S. Hemophilia Treatment Centers (HTCs).  METHODS: Hemophilia Utilization Group Study (HUGS-Va) is a prospective multicenter study evaluating burden of illness and cost of care in persons with hemophilia A in the United States. Patients or parents of patients<18 from six HTCs completed a standardized interview, including demographics, health insurance coverage, barriers to care and treatment pattern. One-year clinical data and two-year dispensing records were abstracted for healthcare and factor utilization. Annual factor use and costs were calculated as the average of two-year data. Generalized linear model with Poisson distribution was used to assess the association between factor replacement and emergency room visits after adjusting for covariates.  RESULTS: Of 329 participants (50% adults), 68% had severe hemophilia. 91% reported using health services at least once during the year: 65% had a HTC comprehensive evaluation, 33% visited a clinician, 21% had physical therapy, 28% visited the emergency room, and 14% were hospitalized. Emergency room visits per person-year were 58% lower among prophylaxis users (versus episodic) after adjusting for age, employment, and insurance coverage (RR=0.42, p=0.002). Patients without inhibitors and severe disease had significantly more factor dispensed (4236u/kg/yr), compared to those with moderate (1089u/kg/yr) or mild (582u/kg/yr) disease (p<0.0001). The average factor cost was $165,188 (median: $104,170) per patient-year in persons without inhibitors and $700,272 (median: $197,621) in patients with inhibitors.  CONCLUSIONS:    Patients access an array of comprehensive health services provided by HTCs. Prophylactic infusion of factor may be associated with decreased healthcare utilization compared to episodic treatment.