Abstract Anesthesia-based pain services are facilitating improvements in the quality of care of surgical patients by developing and directing institution-wide perioperative analgesia programs that include interdisciplinary collaborations. However, the impact of anesthesia-based pain services has not been evaluated in a systematic fashion. This prospective multisite study ( n=23 hospitals) utilized a standardized approach to evaluate the quality of pain care provided to patients who were and who were not cared for by an anesthesia-based pain service. A total of 5837 patients were evaluated using a standardized survey that consisted of a medical record review and a patient interview. The data were collected as part of the hospitals' quality improvement activities. Forty-nine percent of the patients were cared for by an anesthesia-based pain service. Patients who received pain service care reported significantly lower pain intensity scores; had lower levels of pain in the postoperative period; had a lower incidence of pruritus, sedation, and nausea; and experienced significantly less pain than expected. In addition, these patients were more likely to receive patient education about postoperative pain management; were more satisfied with their postoperative pain management; and were discharged sooner from the hospital. The findings from this study demonstrate that the care provided by anesthesia-based pain services has a significant impact on patient outcomes.