A controlled, single blinded study investigated the effect of high velocity manipulation on pressure-pain threshold (PPT) in the thoracic spine in an asymptomatic population. Participants were randomly allocated into intervention groups, and received either a single extension thrust or thirty seconds of sham treatment consisting of 'laser accupuncture". PPT measurements were made using an electric pressure algometer immediately before and after intervention application. Pre- and post-manipulation PPT values were analyzed using a dependent t-test, and emonstrated a significant improvement in the manipulated group (P=0.04) but not in the control group (P=0.88). This study found that a single manipulation did increase thoracic PPT. Further research is warranted to investigate the effect of manipulation on thoracic pain. This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.