In this experiment, we examined the extent to which the spatiotemporal reorganisation of muscle synergies mediates skill acquisition on a two degree-of-freedom (d.f) target acquisition task. Eight participants completed five practice sessions on consecutive days. During each session they practised movements to eight target positions presented via a visual display. The movements required combinations of flexion/extension and pronation/supination of the elbow joint complex. During practice sessions, eight targets displaced 5.4cm from the start position (representing joint excursions of 54°), were presented 16 times. During pre- and post-tests, participants acquired the targets at two distances (3.6cm [36° ] and 7.2cm [72° ]). EMG data were recorded from eight muscles contributing to the movements during the pre- and post-tests. Most targets were acquired more rapidly following the practice period. Performance improvements were, in most target directions, accompanied by increases in the smoothness of the movement trajectories. When target acquisition required movement in both d.f., there were also practice-related decreases in the extent to which the trajectories deviated from a direct path to the target. The contribution of monofunctional muscles (those producing torque in a single d.f.) increased with practice during movements in which they acted as agonists. The activity in bifunctional muscles (those contributing torque in both d.f.) remained at pre-test levels in most movements. The results suggest that performance gains were mediated primarily by changes in the spatial organisation of muscles synergies. These changes were expressed most prominently in terms of the magnitude of activation of the monofunctional muscles.