This article presents recent work investigating the unimolecular dissociation rates of quantum state-selected molecules. Such studies provide the most stringent test for quantitative models of unimolecular reactions and their assumptions. After briefly reviewing the various experimental and theoretical techniques for state-resolved unimolecular dissociation rates, we present results obtained in our laboratory using the method of double resonance overtone photofragment spectroscopy. We focus on the unimolecular dissociation of HOCl as a textbook case in which the dissociation rate is limited by slow intramolecular vibrational energy redistribution and give a simple model to treat this particular class of systems.