The ventral premotor cortex (area F5) plays an important role in the control of hand shape during object grasp. F5 neurones can encode the selection of different grasps, and are excited by vision of graspable objects. However, it is not clear how F5 influences the motor outputs to the hand and arm that control hand shape. In earlier studies in sedated or deeply anaesthetised monkeys, we demonstrated that F5 can exert strong facilitation of corticospinal outputs from primary motor cortex (M1) to the hand (Cerri et al. 2003; Shimazu et al. 2004). We now demonstrate that F5 can give rise to robust modulation of the EMG responses evoked from M1 in the awake monkey performing a visuomotor grasping task. The study was carried out in 2 adult macaques; all procedures were in accordance with the Animals (Scientific Procedures) Act 1986. An object was presented visually to the monkey, and after a variable delay, the monkey was cued to reach, grasp and displace the object. Single bipolar stimuli (100-200 μA) were delivered to pairs of microwires implanted in contralateral F5 and M1. Surgery was performed under deep anaesthesia, induced with 10 mg. kg-1 ketamine i.m. and maintained with 2-2.5% isoflurane in 50:50 O2:N2O; full aseptic procedures were observed and antibiotics and analgesics given postoperatively. Implantation sites were based on prior electrophysiological mapping. EMG responses were recorded during hand shaping and transport prior to object grasp from 4-10 contralateral hand and arm muscles. Single conditioning (C) stimuli delivered to F5, that did not by themselves evoke any detectable EMG response, produced a large facilitation (over twofold) of the EMG-response evoked by test (T) stimuli to M1. Facilitation was observed at short C-T intervals of 0 and 1 ms (Wilcoxon signed-rank p<0.05) and showed a periodicity compatible with I-wave generation (Ziemann & Rothwell, 2000). In contrast to the anaesthetised/sedated macaque, we also saw some suppression of M1 responses by F5. The pattern of facilitation/suppression was muscle specific. Thus F5 can exert robust modulation of M1 outputs to the hand during hand transport and shaping prior to grasp that is specific to particular muscles, and therefore unlikely to reflect a general change in excitability. The modulation of responses probably involves F5-M1 cortico-cortical pathways active during visuomotor transformations underlying object grasp. This study supports F5 as having a role in shaping activity of the hand appropriate for grasp.