Although the great majority of antibiotics are prescribed outside hospitals, little is known about the prevalence and determinants of antibiotic resistance in the group of outpatients. Nasal swabs were taken from 627 consecutive patients aged 40 years or above attending general practitioners in Southern Germany. Staphylococcus aureus was cultured and minimal inhibitory concentrations to various antibiotics were tested. Nasal swabs of 152 patients were positive for S. aureus. Prevalence of resistance was 68·3, 8·3 and 0·7% for penicillin G, erythromycin, and oxacillin respectively. Antibiotic use within the last month was associated with erythromycin resistance [adjusted odds ratio (OR) 7·4; 95% confidence interval (CI) 1·0–53]. Besides a high prevalence of resistance to penicillinase-instable antibiotics we found only one (0·7%) methicillin-resistant S. aureus. Recent antibiotic use was associated with increased resistance to erythromycin.