To estimate the frequency of the use of medicines listed in the Screening Tool to Alert Doctors to the Right Treatment (START) and Screening Tool of Older Person's Prescriptions (STOPP) criteria version 2 among the elderly. A cross-sectional study was conducted on elderly who were attended in medical clinic and cardiology sectors in a hospital in southern Brazil attended at a hospital from February through September 2016. A data-collection tool was used to obtain information on variables, such as demographic and clinical data, and medications used before and during the hospitalization period. The adequacy of the medicines taken was examined with regard to omission (START) or inappropriate use (STOPP). This study was approved by the Research Ethics Committee of the University of Southern Santa Catarina. A total of 307 subjects were included in the final sample. The mean age was 75.2 years (SD = 8; range 65-102). Of the total, 93.5% had had at least one potential prescribing omission (PPO) listed in the START criteria, whereas 95.4% used at least one medicine of the STOPP criteria. PPO was significantly associated with lower mean age (74.9 years, SD = 7.9 versus 79.0 years, SD = 8.8) among the elderly who did not have PPOs detected by the START criteria (p-value=0.03). Furthermore, PPO was associated with longer hospital stay (18 versus 9 days; p-value=0.03). This study revealed inadequate prescription affecting 99.3% of the participating patients. To the best of our knowledge, this was the first to use the START and STOPP criteria, version 2, in Brazil.