Mobilisation is a commonly used technique by osteopaths however there is little evidence to support its efficacy in the treatment of the thoracic spine. This study examined the effect of a single mobilisation (seated extension articulation) intervention in an asymptomatic population. Volunteers were randomly allocated into either a treatment group or a control group (sham laser acupuncture) and pre-intervention pain pressure threshold (PPT) measurements were taken using a pressure electronic algometer on a single thoracic segment. The treatment group received a single application of mobilisation (thirty seconds) and post intervention PPT measurements recorded. Mobilisation applied to the thoracic spine produced a statistically significant increase in PPT while the control group demonstrated no change in PPT. This study supports previous studies that have reported hypoalgesic affects following mobilisation on the cervical and lumbar spine. This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.