['To characterize the use of medicines and to evaluate the inappropriateness of drugs in elderly outpatient population.', 'Twelve community pharmacies in different districts of Lisbon-Portugal.', 'Observational cross-sectional survey, in a sample of 213 elderly outpatients (age>or=65-years-old) presenting a prescription with two or more drugs, for their own use.', 'Drug use pattern and prevalence of potentially inappropriate medication.', 'We have studied 213 outpatients, who were taking a total of 1,543 drugs, with an average of 7.23 per patient. The drugs were distributed mainly in the following 3 ATC (Anatomical Therapeutic Chemical Classification) classes: C (cardiovascular system), N (nervous system) and A (alimentary tract). Using the 1997 Beers Explicit criteria, 75 occurrences of inappropriate medicines were detected in 59 patients (27.7%), while with the 2003 Beers Explicit criteria we detected 114 cases of inappropriate medication in 82 patients (38.5%). The occurrence of inappropriate medicines was significantly associated with the consumption of a high number of drugs. According to the ATC Classification, more than one half of the cases of inappropriateness were related with long acting benzodiazepines and with ticlopidine. The 2003 version detected a significantly higher prevalence of inappropriate drug use having potentially adverse outcomes of high severity.'] Do inappropriate drug use by Portuguese elderly outpatients -- effect of the Beers criteria update?