Recent animal studies have shown strong facilitation from ventral premotor cortex (area F5) on late I-wave components evoked by test stimuli applied to motor cortex. (Shimazu et al., 2004). To investigate a possible grasping-related modulation of the late I-waves in humans we used a TMS paired pulse paradigm (Ziemann et al., 1998) that selectively facilitates I-wave components of the MEP. Volunteers (thirty right-handed subjects, aged 19-32) were randomly presented with one of two different objects: a disc or a vertically oriented handle. The subjects were instructed to grasp the object or remain at rest in response to an auditory cue. Surface EMG activity recorded from the right 1DI and ADM muscles during the grasp showed high specificity of individual muscle activity for the grasped object (ANOVA p=0.0001). Single or paired (first stimulus suprathreshold and second subthreshold) TMS pulses were delivered to the left motor cortex through a figure-of-eight coil at interstimulus intervals (ISI) of 1.3, 2.1, 2.5, 3.3 and 4.1 ms, during object presentation with the hand at rest. We found a clear and highly significant modulation of the MEP obtained with the 2.5 ms ISI that showed a significant interaction between object and muscle (ANOVA p=0.001). This enhancement preceded the grasping movement by at least 600 ms and was correlated significantly with the subsequent EMG activity for hand shaping prior to object contact (t-test, ADM p<0.05; 1DI p<0.05). Control experiments showed no modulation was found during object presentation alone, during mental imagery of the grasp action or during the performance of non-object driven movements which employ a similar pattern of muscle activity. Our study has pinpointed significant facilitation at an ISI of 2.5 ms, which is likely to reflect augmented I2 corticospinal activity, in the period preceding a planned grasp. This approach allows us to investigate a specific cortico-cortical mechanism that probably subserves the transformation of cortical representation of the geometrical properties of an object to grasp-specific outputs from motor cortex that shape the hand.