In recent years, mass spectrometry has evolved into a viable tool for interrogating the stoichiometry and structures of large, multimeric protein complexes. Following electrospray ionization these assemblies can be dissociated via multiple low energy collisions with inert gas molecules (i.e. collision induced dissociation, CID). Using this general approach a wide array of macromolecular assemblies have been studied. Despite the prevalence of multiple collision CID it is limited by a poorly understood phenomenon in which dissociation is dominated by highly asymmetric mass and charge partitioning. In nearly every system studied so far, no matter what its size, CID results in the ejection of only a monomer that carries away approximately half of the initial charge of the complex. In the present study we have employed surface induced dissociation (SID) to fragment several protein complexes, and compared it to CID in the same extended m/z range QTOF, to improve our fundamental understanding of the dissociation of protein complexes. Activation by SID involves a single collision in contrast to the multiple collisions of CID. In SID spectra of several complexes, including dimers of cytochrome C, and tetramers of transthyretin, hemoglobin, and concanavalin A we have observed remarkably symmetric dissociation products with respect to both charge and mass. We propose here that, unlike CID, SID reaches a dissociative state prior to significant unfolding of the ejected subunit.