OBJECTIVES: Polypharmacy in elderly patients has grown in the last decade giving place to new therapeutic and economic challenges. The aim of this study was to characterize the nature of polypharmacy and to identify associated direct drug costs. METHODS: A community pharmacy based cross-sectional study was carried out using the brown-bag review methodology. Elderly patients (≥65 years old) currently taking 4 or more drugs were invited to participate in the study. Drugs were classified using ATC codes and costs were identified as the retail prices. SAS Guide version 4.0 was used for statistical analysis, 95% confidence intervals for the average costs per patient and Mann-Whitney Wilcoxon test to identify differences between expenditure patterns were used. RESULTS: A total of 1597 patients (66% women, mean age 74.5 ± 6.4 years) were recruited in 158 pharmacies. Average medicines consumption was found to be 7.6 per patient. Mean daily cost per patient was €3.2 (CI 95%: 3.1-3.3). Differences in costs according to age, gender, educational level or residential area were not statistically significant. Sinvastatin, omeprazol and clopidogrel were identified as the most costly drugs. CONCLUSIONS: Polypharmacy was found to be highly prevalente amongst Portuguese elderly population. Associated direct daily drug costs in these patients were found to be three times higher when compared to the general population.