This paper investigates the determinants of regional variations in outpatient antibiotic consumption using Swiss data. The analysis contributes to the debate on appropriate antibiotic use by improving the understanding of its determinants, and may help to define more effective health care policies to reduce the resistance phenomenon. Findings suggest that Switzerland exhibits relatively low levels of consumption among European countries. There are significant differences between cantons both in the per capita antibiotic sales and defined daily doses per 1000 inhabitants (DID). Econometric estimations suggest that DID are significantly related to per capita income, antibiotic price, the density of medical practices, demographic, cultural and educational factors. The incidence of bacterial infections is also relevant. Appropriate policies affecting antibiotic consumption in the community can be designed by looking at crucial determinants in the model and their related impact.