Inappropriate antibiotic use in primary care, such as in Respiratory Tract Infections (RTIs), is an important cause of bacterial resistance. This study aimed at describing the current pattern of outpatient antibiotic use in acute RTIs in Spain and evaluating adherence to national recommendations. A retrospective observational study was performed including all the episodes of RTIs registered during a 1-year period in a north-eastern Spanish region. Data related to patient demography, diagnoses and antibiotic prescriptions were collected from the electronic medical history database in the region, and adherence to recommendations for antibiotic prescribing was assessed. One third of patients with a RTI were prescribed an antibiotic, with young adults (aged 15-64 years) being the most treated. High prescribing rates were observed in patients with acute otitis, sinusitis and acute tonsillitis (about 70%), whereas low rates were found in acute bronchitis (50%) and non-specific upper RTIs (24%) episodes. A high prescription of broad-spectrum agents and antibiotics not recommended as first choice was observed. In accordance with Spanish guidelines, there exists a potential over-prescribing of antibiotics for all the diagnoses studied, especially in the adult population. Moreover, the choice of antibiotics is frequently based on agents with a high risk of increasing antimicrobial resistance. Multifaceted strategies should be implemented in order to improve the quality of antibiotic prescribing in primary care.This article is protected by copyright. All rights reserved.