Standard verbal or analogue scales may not be accurate to assess acute postoperative pain in elderly patients. This study was designed to field test the Algoplus tool, developed specifically for this population and based on observation of patient behavior. Prospective, observational cohort. Single center, French University hospital. Forty-eight patients, aged over 65, scheduled for surgery under general anesthesia, and observed on admission to the postanesthesia care unit, immediately after extubation, during the different steps of analgesic intervention (demand, relief with intravenous opioid titration, plus intermediate measures when relevant), and either at discharge or 3 hours after admission. A numerical rating scale (NRS) was used to guide analgesia. The Algoplus score and the state of alertness or sedation were noted. NRS scores and Algoplus scores were significantly related, and both scores significantly decreased under the effect of analgesia, but the correlation was low. In early observations, the Algoplus score was higher than that predicted by the NRS score, in relation to residual sedation. Female gender tended to lower the Algoplus score compared to the NRS score. When the NRS score exceeded 3/10, indicating the need for analgesic intervention, the Algoplus score was generally lower than the recommended trigger for analgesia (2/5). These results are promising, but further evidence of a clinical benefit to the use of Algoplus for acute postoperative pain is needed. In future studies, scoring should be adjusted to take into account the time from extubation, the state of sedation, and the patient's gender in order to interpret results.