The main purpose of this study was to describe and interpret the COP trajectory during barefoot running in a large cohort of young adults with no history of injury. COP data were collected from 215 subjects, who ran at 3.3 ms(-1) over a 16.5m long track, with a built in Footscan pressure platform. COP data were filtered using a 50 Hz lowpass butterworth filter and normalised. Reliability was then studied and mean curves were calculated for medial-lateral displacement (COP(x)) and velocity (v(x)COP), anterior-posterior displacement (COP(y)) and velocity (v(y)COP) as well as for the resultant velocity (v(xy)COP). Displacement and velocity of the COP provided insight over functional foot behaviour. A medially oriented peak in v(x)COP was found, which may reflect the fast initial pronation. A laterally oriented second peak in v(x)COP, together with a second peak in v(y)COP, indicated a fast forward shift of the COP over the lateral border of the foot during forefoot contact phase. During the forefoot push off phase, at the level of the metatarsals, anterior velocities of the COP were low and reflected the importance of the forefoot during push off. Finally, the COP course was studied for high arch, normal and low arch feet and indicated, a more lateral COP course for the low arch feet.