Background Medications in which the risk of adverse events exceeds the expectations of clinical benefits are called potentially inappropriate medications (PIMs). To identify the use of PIMs in elderly patients, the most commonly used tool are the Beers criteria, developed for the population of the United States. Recently, a consensus panel of Argentine experts developed the first Latin American tool, called the IFAsPIAM List. Objective The present study aimed to identify PIM prescriptions in elderly outpatients, to estimate the prevalence of PIMs, and to evaluate their possible relation with polypharmacy and gender and age of the patients. Also, we aimed to compare the results obtained by using the Beers criteria and the IFAsPIAM List. Setting Ten community pharmacies of Rosario, Santa Fe, Argentina. Methods A cross-sectional observational study was conducted between February and September 2015. Data were acquired from 56,952 prescriptions prescribed to 2231 patients aged 65 years old or older. To detect the use of PIMs, we used two tools: the Beers criteria and the IFAsPIAM List. Main outcome measure The prevalence of PIM use according to the Beers criteria and the IFAsPIAM List. Results The monthly average of medications dispensed per patient was 4.35 ± 2.18 and 42.27% of the patients presented major polypharmacy. The prevalence of PIMs was 72.75% according to the Beers criteria and 71.13% according to the IFAsPIAM List (Kappa coefficient k = 0.72), and was significantly higher in patients with major polypharmacy, older than 75 years old, and females. The most frequent PIMs prescribed were anxiolytics, analgesics and antipsychotics. Conclusions The IFAsPIAM List is an effective tool to evaluate the prescription of PIMs in the elderly. The results showed a high prevalence of PIMs with a multicausal origin and directly associated with polypharmacy. As clarified by the authors of the IFAsPIAM List, the criteria specified in the list do not substitute the clinical evaluation of each patient.