Seating is an active area of ergonomics research; however, little research has been performed that evaluates seated body postures for a variety of tasks and chairs. The goal of this study was to evaluate the effects of common office tasks on head, upper extremity, torso, hip, and leg postures. Prolonged awkward postures may contribute to musculoskeletal pain and disorders. Twenty-five participants performed four office tasks using four office chairs while postures were recorded using a 3D optical marker system. The tasks were typing on a desk fixed at 73.7cm (29“), typing with the desk adjusted to be slightly above elbow height, reclined movie watching, and a forward leaning writing task. Head angle, pelvis-to-head angle, thoracic cage angle, and pelvis angle were all significantly different between tasks (p = <0.0001). This method for full body posture measurement will allow further research into the effects of tasks and chairs on seated posture.