Lumbar spine dysfunction has been shown to decrease postural stability. It has been hypothesized that applying manual therapy to the lumbar spine may have an effect on improving postural stability. The aim of this study was to investigate the effects of an osteopathic manipulative therapy (OMT) treatment protocol applied to the lumbar spine on postural stability as measured by average centre of pressure velocity (COPV) on a vertical force platfrom measurement system. Significant reduction in average COPV was demonstrated during tandem stance for the intervention group with both eyes-open and eyes-closed. No significant changes in average COPV were observed during bipedal or unipedal stance for either group. Results of this study suggest that OMT applied to the lumbar spine may have an effect on postural stability. Further research with a larger sample size, symptomatic patients and a longer-term treatment protocol is needed to extrapolate these findings into the clinical setting. This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.