There is a growing concern in the United States regarding antibiotic resistance due to inappropriate prescribing of antibiotics. OBJECTIVES: Report the patterns of oral antibiotics filled following a medical visit for upper respiratory infection (URI) in a state Medicaid population. METHODS: The study sample included Medicaid recipients who had an outpatient or emergency department (ED) visit in 2002 for an acute URI. Outpatient and ED claims with a primary ICD-9-CM diagnosis code for acute nasopharyngitis, acute pharyngitis, acute URI, acute bronchitis, or influenza were extracted. Prescription claims for antibiotics filled within five days following a URI-related medical visit also were extracted. RESULTS: A total of 21,163 recipients were included in the study. Over 71% of the recipients were female, and nearly 95% were white. Recipients between 21 to 44 years of age accounted for more than half of the study group. Nearly half of all recipients made only one visit for URI throughout the year, and over 28% made 3 or more visits. Oral antibiotics accounted for roughly 10% of the total prescriptions filled within 5 days following an acute URI-related medical visit. These antibiotics were for penicillins (41%), cephalosporins (15%), macrolides (11%), and others including quinolones, tetracyclines, sulfonamides and trimethoprim (33%). CONCLUSION: One out of every ten prescriptions filled following an acute URI-related medical visit among recipients of Medicaid was for an oral antibiotic. Many upper respiratory tract infections are viral in nature, in which oral antibiotic treatment may be inappropriate.