All previously reported CAAX-based farnesyltransferase inhibitors contain a thiol functionality. We report that attachment of the 4-imidazolyl group, via 1-, 2-, or 3-carbon alkyl or alkanoyl spacers, to Val-Tic-Met or tLeu-Tic-Gln provides potent FT inhibitors. (R*)-N-[[1,2,3,4-Tetrahydro-2-[N-[2-(1H-imidazol-4-yl)ethyl] -L-valyl]-3-isoquinolinyl]carbonyl]-L-methionine ([imidazol- 4-yl-ethyl]-Val-Tic-Met), with FT IC50 = 0.79 nM, displayed potent cell activity in the absence of prodrug formation (SAG EC50 = 3.8 muM).