The purpose of this study was to evaluate pain scores and plasma beta-endorphin levels following a single spinal adjustive manipulation in subjects with acute low back pain. Eighteen subjects were randomly assigned to either a control group, which received no treatment; a sham group, which received only light physical contact (touch); or an experimental group, which received an adjustive manipulation at a specific lumbar segment. Following a standard protocol, all subjects were administered visual analog pain scales and venous blood was drawn 5 min prior to, 5 min after, and 30 min after intervention. Analysis of the pain scores indicated that there was a slight, but significant, reduction of pain in the experimental group, but no similar reduction in the control or sham groups. Furthermore, this reduction of pain in the experimental group was not accompanied any significant change in the plasma beta-endorphin concentration.