Ageing is a complex process. As we age, significant physiological changes occur and the incidence of multiple organic and systemic pathologies increases. Older patients are prescribed a high number of drugs. The elderly are also the group with the greatest number of medical appointments and hospital admissions. Seniors are the population group with the highest level of polymedication. Polymedication generates a high cost for the National Health System and can also increase the number of adverse reactions or interaction with medications. The inappropriate prescribing of drugs is a frequent problem among elderly people, which contributes to increasing the risk of ADR. In recent years, several tools have been developed to detect potentially inappropriate prescriptions in older adults. The aim of this review is to describe two of these tools: the North American BEERS criteria and the European STOPP (Screening Tool of Older Person’s Prescriptions)/START (Screening Tool to Alert doctors to Right i.e. appropriate, indicated Treatment) criteria. The STOPP criteria offer the added value of detecting not only inappropriate prescription of certain drugs, but also the lack of prescription of indicated drugs. The STOPP/START criteria can become a good tool for improving prescriptions among older patients.