BACKGROUND: Potentially inappropriate medications (PIMs) are medications contra-indicated in particular circumstances. We sought to characterize PIMs by level of polypharmacy by age, sex and race/ethnicity. METHODS: We performed a cross-sectional drug dispensing study using electronic health records available through the US Department of Veterans Affairs. We extracted pharmacy fill and refill records during fiscal year 2016 (i.e., October 1, 2015 - September 30, 2016) for all patients aged 49 to 70 who accessed care in the preceding fiscal year. PIMs were defined by the combined Beers and Laroche (henceforth Beers Laroche) criteria used for older patients and the PROMPT criteria used for middle-aged. RESULTS: In the 1 499 586 patients aged 49-64, PIMs prevalence by PROMPT in patients with 0-4, 5-9 and ≥10 medications was 14.0%, 62.2% and 86.1%, respectively, and by Beers Laroche was 14.3%, 63.4% and 85.7%, respectively. In the 1 249 119 patients aged 65-70, PIMs prevalence by Beers Laroche was 14.8%, 59.9% and 83.3%, and by PROMPT was 13.9%, 57.4% and 82.0%, respectively. Meaningful differences in prevalence were shown by sex and race/ethnicity according to both set of criteria (e.g. PROMPT in patients with 5-9 medications: 66.1% women vs. 59.3% men; Standardized-mean-differences (SMD) = 0.14; 61.7% of White vs. 54.5% of non-White; SMD= 0.15). The most common PIMs were digestive, analgesic, antidiabetic and psychotropic medications. CONCLUSION: Prevalence of PIMs was high and increased with polypharmacy. Beers Laroche and PROMPT provided similar estimation inside and outside their target age, suggesting that PIMS are common among those with polypharmacy regardless of age.Read less <