BACKGROUND: Retail clinics are an increasingly popular source for medical care. Concerns have been raised about the effect of these clinics on the cost, quality, and delivery of preventive care. OBJECTIVE: To compare the care received at retail clinics for 3 acute conditions with that received at other care settings. DESIGN: Claims data from 2005 and 2006 from the health plan were aggregated into care episodes (units that included initial and follow-up visits, pharmaceuticals, and ancillary tests). After 2100 episodes (700 each) were identified in which otitis media, pharyngitis, and urinary tract infection (UTI) were treated first in retail clinics, these episodes were matched with other episodes in which these illnesses were treated first in physician offices, urgent care centers, or emergency departments. SETTING: Enrollees of a large Minnesota health plan. PATIENTS: Enrollees who received care for otitis media, pharyngitis, or UTI. MEASUREMENTS: Costs per episode, performance on 14 quality indicators, and receipt of 7 preventive care services at the initial appointment or subsequent 3 months. RESULTS: Overall costs of care for episodes initiated at retail clinics were substantially lower than those of matched episodes initiated at physician offices, urgent care centers, and emergency departments ($110 vs. $166, $156, and $570, respectively; P < 0.001 for each comparison). Prescription costs were similar in retail clinics, physician offices, and urgent care centers ($21, $21, and $22), as were aggregate quality scores (63.6%, 61.0%, and 62.6%) and patient's receipt of preventive care (14.5%, 14.2%, and 13.7%) (P > 0.05 vs. retail clinics). In emergency departments, average prescription costs were higher and aggregate quality scores were significantly lower than in other settings. LIMITATIONS: A limited number of quality measures and preventive care services were studied. Despite matching, patients at different care sites might differ in their severity of illness. CONCLUSION: Retail clinics provide less costly treatment than physician offices or urgent care centers for 3 common illnesses, with no apparent adverse effect on quality of care or delivery of preventive care. PRIMARY FUNDING SOURCE: California HealthCare Foundation.