Acute traumatic injury engenders the production of beta-endorphin (BE) and other endogenous opioids. Elevated BE concentration putatively correlates with pain perception in trauma patients. The authors examined traumatic injury severity, pain perception, and BE concentration in patients admitted to an urban trauma center. Brief rating instruments for pain and unpleasantness were administered, and blood was drawn for BE analysis in 48 trauma admissions and 33 age-, gender-, and race-matched control subjects for comparison. The authors found no correlation between severity of pain perception and BE, but a significant correlation was found between BE and patient body weight (P < 0.05), physician pain rating (P < 0.01), and Injury Severity Score (P < 0.001). The results suggest that past findings associating trauma pain perception and BE concentration are spurious.