Homologs of the tumor suppressor p53, called p63 and p73, have been identified. The p63 and p73 family members possess a domain structure similar to p53, but contain variable C-terminal extensions. We find that some of the C-terminal extensions contain Sterile Alpha Motif (SAM) domains. SAM domains are protein modules that are involved in protein-protein interactions. Consistent with this role, the C-terminal SAM domains of the p63 and p73 may regulate function by recruiting other protein effectors.