By regulating the structure of chromatin, ATP-dependent chromatin remodeling complexes (remodelers) perform critical functions in the maintenance, transmission and expression of the eukaryotic genome. Although all known chromatin-remodeling complexes contain an ATPase as a central motor subunit, a number of distinct classes have been recognized. Recent studies have emphasized a more extensive functional diversification among closely related chromatin remodeling complexes than previously anticipated. Here, we discuss recent insights in the functional differences between two evolutionary conserved subclasses of SWI/SNF-related chromatin remodeling factors. One subfamily comprises yeast SWI/SNF, fly BAP and mammalian BAF, whereas the other subfamily includes yeast RSC, fly PBAP and mammalian PBAF. We review the subunit composition, conserved protein modules and biological functions of each of these subclasses of SWI/SNF remodelers. In particular, we will focus on the roles of specific subunits in developmental gene control and human diseases. Recent findings suggest that functional diversification among SWI/SNF complexes allows the eukaryotic cell to fine-tune and integrate the execution of diverse biological programs involving the expression, maintenance and duplication of its genome.