Many unimolecular mass spectrometric fragmentations do not occur directly from the ionized but otherwise intact molecules, but involve isomerization to reactive intermediates as the critical step of the fragmentation mechanism. During the last few years, distonic ions and ion/neutral complexes have been identified as important intermediates of mass spectrometric fragmentations. Examples are taken from the recent literature and from our own unpublished results to illuminate the role of these intermediates, in particular for rearrangement reactions by remote group interaction.