The prevalence of sinusitis has been increasing, as has been the number of visits for the condition. Relatively little data are available on its diagnosis, treatment and costs. OBJECTIVE: The purpose of this study is to analyze resources utilized in the treatment of sinusitis, in particular recurrent sinusitis. METHODS: The database of Fallon Community Health Plan (FCHP), a Massachusetts based group model HMO, was analyzed to identify members with three or more visits for sinusitis in an eighteen month period. A total of 495 patients were identified. Their utilization of primary care physician (PCP) and specialty visits, procedures, ancillary services, costs of services, type, quantity, and cost of drugs prescribed was analyzed. RESULTS: 76% of the patients were women and 24% were men. Age ranged between 18 years and 91 years (mean=45). The subjects had a total of 17,407 procedures and diagnoses during the study period. In 31% of visits, the subjects were treated by a PCP; in 8.5% visits they were seen by an Allergist; and in 6.7% visits they were seen by an ENT. The most frequent primary diagnosis was Allergic rhinitis (8.2%) followed by acute sinusitis (5.8%). The total cost of the utilization was $1,052,678 (mean=$2127). The total number of prescriptions filled during the study period was 13,539 (mean=27.35). The total cost of these prescriptions was $446,879 (mean=$903). CONCLUSION: The treatment and management of patients with chronic sinusitis is more intensive than commonly realized. The present study provides insight into demographics and the type and costs of treatment of this patient group.