Delamination of polymer/glass interfaces was studied under cyclic and monotonic loading using an interfacial, four-paint flexure sandwich specimen. Specifically, crack growth rates along epoxy acrylate/glass interfaces were characterized over a range of velocities from 10(-9) to 10(-6) m/s as a function of low (10-20% RH) and high (75-80% RH) humidities. For low humidities, interfacial crack growth rates under cyclic loading are almost two orders of magnitude greater than those under monotonic loading with energy release rates G = G(max) of the cyclic loading. At high humidities, interfacial crack growth rates under monotonic loading are approximately equal to cyclic fatigue crack growth rates at low humidity.