Gene duplication and diversification can provide the raw material for the evolution of new morphologies. In plants, the numbers of MADS-box genes have multiplied considerably, resulting in a plethora of these transcriptional regulators in the angiosperms (flowering plants). MADS-box genes have been implicated in the regulation of a variety of flower developmental processes; therefore, understanding the functional consequences of duplication and diversification in this gene family can shed light on the evolution of different floral forms. Recent functional analyses of MADS-box gene lineages have demonstrated that in various instances these genes have swapped roles, acquired novel roles, or retained ancestral roles. These studies underscore the idea that gene function cannot be extrapolated from structural orthology.