Interest in studying human posture, movement, and physical activity is growing due in part to the increasing prevalence of obesity. Accelerometers are commonly used in motion analysis systems to enable researchers to conduct studies outside of the traditional laboratory environment; however the available systems tend to be bulky and unsuitable for long-term studies. Therefore, a need exists for a physically robust, yet compact motion analysis system that can be easily worn for an extended time period without disrupting the person?s range of motion. Here we describe our on-going efforts to develop a robust, compact system that can measure body posture and movement using a tri-axial accelerometer, and then store this data on a secure digital memory card. This device can be easily configured to collect accelerometer data for specific applications in human motion analysis. In the future, this device will be used to study physical activity in free-living individuals.