Extensive new data, which reveal the statistical nature of the dissociation process of ammonia cluster ions following multiphoton ionization, are presented. Measured values of the evaporative unimolecular rates and the kinetic energy releases are used to determine binding energies of ammonia cluster ions. The appearance of magic numbers in the distribution of cluster ion abundances is discussed in terms of the thermochemical stability of the cluster ions and the concomitant effects expected on their metastable dissociation rates. Common behaviour is noted for other cluster systems, such as CH3OH and (CH3)2CO. However, at certain degrees of aggregation, these systems are found to exhibit particular ‘solvent-driven’ dissociation channels.