OBJECTIVES: To compare characteristics of patients with diagnosed allergic rhinitis (AR) by quartiles of health care costs. METHODS: Patients 12-64 years of age  with ≥2 AR diagnoses or ≥1 diagnosis and ≥1 AR-related prescription claim  continuously eligible for 12 months before and 12 months after an AR diagnosis (1/1/2008-3/31/2011) were identified from a privately-insured claims database (N~14,000,000). The index date was defined as the most recent AR diagnosis date meeting the eligibility criteria, baseline period as 12 months before, and study period as 12 months after the index date. Descriptive analyses compared demographic characteristics, co-morbidities, healthcare resource utilization and costs (inflated to 2010 dollars) among patients in different quartiles of study period health care costs. RESULTS: A total of 146,597 patients met the inclusion criteria. Health care costs per patient ranged from $0-$1,118 for the lowest quartile(Q1) to $6,349-$1,059,699 for the top quartile(Q4). Q4 patients were significantly(p<0.05) older (age 46 vs. 44[Q3], 40[Q2], 36[Q1]), had significantly higher proportion of women (66.5% vs. 62.6%, 56.7%, 43.9%), had more co-morbid conditions (e.g., sinusitis, asthma, depression, sleep apnea), and used significantly more medications (13.4 vs. 8.8, 6.1, 3.7) at baseline than patients in lower quartiles. During the study period, Q4 patients had significantly higher rates of inpatient visits (26.7% vs. 3.4%, 1.2%, 0.6%), emergency department visits, outpatient/other days, and prescription drug use, as well as higher healthcare costs ($19,519 vs. $4,186, $1,798, $544), and they accounted for 75% of health care costs among AR patients. Additionally, Q4 patients had the highest AR-related costs ($662 vs. $521, $345, $155) and accounted for 40% of AR-related costs among AR patients. CONCLUSIONS: Health care costs for patients with AR were highly variable, with patients in the top quartile responsible for the majority of costs. High cost AR patients were older, had higher proportions of co-morbid conditions and higher health care resource utilization than lower cost AR patients.