OBJECTIVES: The 2006 guidelines of the American Academy of Family Physicians recommends to avoid prescribing of antibiotics to patients diagnosed with nasopharyngitis, acute upper respiratory tract infections (ARTI) or acute bronchitis. Inappropriate prescribing of antibiotics to patients can lead to a rise in antibiotic-resistant bacteria and subsequently increase the economic burden.  The purpose of this study was to determine the trends in the antibiotic prescribing rates for adults diagnosed with nasopharyngitis, acute bronchitis or ARTIs in ambulatory care settings in United States after the 2006 guidelines. METHODS: This was a retrospective, cross-sectional analysis of the representative national survey of office visits from the National Ambulatory Medical Care Survey for the years 2006 to 2008. Adults≥18 years of age with a diagnosis of nasopharyngitis, ARTIs, or acute bronchitis were identified using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes. Inappropriate antibiotic prescribing rates for the three conditions were calculated separately and collectively. Descriptive analysis was conducted to determine the utilization patterns by patient and physician characteristics. Logistic regression was carried out to determine the trends in the antibiotic utilization. RESULTS: Analysis of multiyear data showed no statistically significant trend (p-value = 0.4622) in the antibiotic prescribing rates from 2006 to 2008. Approximately, 45.26 million office visits annually resulted in a primary diagnosis of nasopharyngitis, acute URI, or acute bronchitis; of these visits, 1.5%, 44%, and 61%, respectively, resulted in the prescribing of an antibiotic. Overall 47.26 % of the study population was prescribed antibiotics. CONCLUSIONS: Antibiotic prescription rate did not change significantly from 2006 to 2008. Antibiotics were prescribed inappropriately in 47% of the adults diagnosed with nasopharyngitis, ARTI, or acute bronchitis. Concerted efforts are needed to improve antibiotic prescribing practices for these conditions.