The Griffith and stability criteria for the blister test have been derived from thermodynamic arguments. The Griffith criterion includes the stored energy in the blister as well as the interfacial energy change associated with debonding. Based on these criteria an analysis is given of a blister test with a neo-Hookian overlayer debonding: from a rigid substrate. A closed analytic form for the strain energy release rate, G, is obtained valid for large elastic deformation of a thin circular him. The criteria derived indicate that quasi-static debonding of the blister is always stable, independent of the interfacial energies and the extent of blister deformation.