The aging of the population is a global trend but especially in developed societies. One of the factors affecting their quality of life is the number of drugs they take. This population group represents approximately 17% of the total and it's responsible for 70% of drug spending. The prevalence of polypharmacy in the elderly is increasing in our society and its incidence depends on several factors. The main objective of this study is to know the prevalence of polypharmacy in a nursing home related to variables such as sex, age or their level of dependence. Polypharmacy is defined as taking of 5 or more drugs in a chronic way. A cross-sectional descriptive study was carried out from a sample of 91 residents, with an average age of 85.89 years (+/- 7.06), and are institutionalized an average of 5.43 years. The medical records have been used, with prior authorization from the center, and data have been treated using the statistical package SPSS Statistics and Excel. A total of 718 drugs from 197 different active substances are prescribed. The polypharmacy prevalence is 83.1%. The average of active ingredients per resident is 7.9 (+/- 3.55). Males take an average of 7.51 (+/- 3.6) drugs, and females take 8.19 (+/- 3.5). Using the Anatomic ATC classification, the most prescribed drugs are those associated with the nervous system, with a prevalence of 32.6%, and are consumed by 85.5% of the sample, following of the alimentary tract and metabolism (with 26.9%), prescribed to 94.5%. According to the Therapeutic ATC classification, the five most prescribed subgroups are: Agents for the treatment of acid-related disorders (prevalence of 11.0% and prescribed to 86.8% of the sample), psychoanalytics (10.6% / 54.9%), psycholeptics (9.3% / 57.1%), analgesics (7.2% / 48.4%) and diuretics (7.0% / 45.1%). The results coincide with other studies, although there is a higher prevalence in the polypharmacy due to the high average age and the fact of being institutionalized.