The experimental results from implosion tests of various graphite/epoxy and glass/epoxy cylinders are correlated with predictions from a performance model for thick composite cylinders subjected to external hydrostatic pressure. That performance model consists of a stress module, a stability module, and a material failure module. The stress module predicts the ply-level stresses and is based on an anisotropic elasticity solution for axisymmetric loading. The stability module predicts the critical buckling load based on a laminated orthotropic shell theory which includes transverse shear deformations. The failure module rotates the ply-level stresses computed from the stress module to the principal material coordinates and applies several existing failure criteria for determining first-ply failure. The correlation between the experimental data and analytical results led to the selection of the Hashin criteria as the most appropriate failure theory for thick-laminated composite cylinders loaded in compression. The results obtained from the Hashin criteria are consistent with the observed experimental results provided that composite material strength allowables are based on representative tests and that appropriate solutions for cylinder stresses are used. Both the failure criteria and stress solution must allow for the three-dimensional stress state and for the discrete layer construction. Further applications of the performance model are demonstrated for a range of laminate constructions. The results from these parametric studies provide insight to optimum designs for graphite/epoxy and glass/epoxy cylinders.