Large tensile deformation behavior of the alloy of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) are experimentally investigated in this paper. Based on the adaptations of digital image correlation (DIC) method suitable for large inhomogeneous deformation in three dimensions, a new displacement measurement system is developed. Using the new displacement measurement system, we obtain the displacement fields in PC/ABS alloy. Such that variations of the strain and strain rate during tension process, and the true stress strain curves for PC/ABS alloy are derived. Also, volume variation of PC/ABS alloy is also discussed. Moreover, in situ scanning electron microscopic (SEM) observation is carried out to study the micro-mechanism of large inhomogeneous deformation of PC/ABS alloy. It is seen that contraction rate of specimen thickness is bigger than that of the width of specimen during plastic deformation. The axial tensile strain rate is much higher in the necking region. It should be noted that the local volume increases with the increase of axial true strain to a certain value, after that it decreases. Initiation and growth of crazes are the main mechanism of tensile deformation of PC/ABS alloy after yielding. (c) 2006 Elsevier Ltd. All rights reserved.