Prediction of the energy release rate (ERR) and its components for mixed-mode delamination of composite laminates is discussed. A classical plate theory (CPT) version of Irwin’s virtual crack closure method is developed and used for the ERR, first for plane strain and then for three-dimensional deformations. It is shown that CPT does not provide quite enough information to obtain a decomposition of ERR into its opening and shearing mode components. Results from a continuum analysis are needed to complete the decomposition; but analysis of only one loading case is required for two-dimensional and certain three-dimensional problems. In two example problems the finite element method is used with CPT to complete the mode decomposition. Results from CPT and the finite element method are then compared for several cases.