Abstract Objective. To assess the potential overprescribing in patients with acute rhinosinusitis across six countries with different antibiotic prescribing rates and different prevalence of antibiotic resistance. Design, setting and subjects. A cross-sectional study including GPs from two Nordic countries, two Baltic countries and two Hispano-American countries registered patients with respiratory tract infections (RTIs) during three weeks in January 2008 as part of the EU-funded project "Health Alliance for Prudent Prescribing, Yield And Use of antimicrobial Drugs In the Treatment of respiratory tract infections" (HAPPY AUDIT). Main outcome measures. Use of antibiotics for acute rhinosinusitis based on the recommendations in the European Position Paper on Rhinosinusitis and Nasal Polyps 2007 (EP3OS). Results. In total, 618 participating GPs registered 33 273 patients with RTI of whom 1150 (3.46%) were considered to have acute rhinosinusitis. Over 50% of the patients with acute rhinosinusitis had symptoms for < 5 days and 81% were prescribed antibiotics. In total, 68% of the patients included were not prescribed antibiotics according to guidelines; 45% had symptoms < 5 days or no fever (possible overprescribing) and 23% had symptoms < 5 days and no fever (probable overprescribing). Conclusion. A considerable number of patients with symptoms of acute rhinosinusitis were not managed according to European recommendations (EP3OS guidelines). To prevent overprescribing, efforts should be made to implement the recommendations in daily practice.