We used a TAP-tag approach to identify candidate binding proteins for the related Ras family GTPases: H-Ras, R-Ras, and Rap1A. Protein complexes were isolated from mouse fibroblasts, and component proteins were identified by a combination of nanoflow HPLC and tandem mass spectrometry. H-Ras was found to associate with numerous cytoskeletal proteins including talin-1. R-Ras and Rap1A each associated with various signaling molecules, many of which are membrane-associated. Thus, we have established the first database of potential Ras interactors in mammalian cells.