When particle systems are in the collisional regime normal impacts are rare events. Oblique impacts are the norm and are much more complex due to the tangential elastic interaction. The collisional behaviour and subsequent rebound kinematics due to impact are further complicated by particle rotations prior to the impact event. Almost all previous published work on particle impact have ignored the effect of initial particle spin. In this paper we demonstrate that all the aspects of the rebound kinematics can be normalised by considering an effective impact angle that is defined by the ratio of the relative initial tangential to normal surface velocities of the two impacting bodies. (C) 2009 Elsevier B.V. All rights reserved.