The enzymatic degradation of poly(3-caprolactone) (PCL) has been investigated by using quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR) in situ. The frequency and dissipation responses of QCM-D and the SPR signal responses can well describe the weight loss and the morphological changes of a PCL film. Our experiments reveal that the degradation has much dependence on the crystallinity and morphology of PCL. PCL with lower crystallinity (45%) and small spherulites degrades in a way of layer-by-layer. Both QCM-D and SPR measurements demonstrate that the degradation is of first-order. However, PCL with higher crystallinity (55%) and larger spherulites exhibits a more complex degradation behavior, namely, the degradation in crystalline region lags behind than that in amorphous region, leading to a microporous structure. 2007 Elsevier Ltd. All rights reserved.