The potential energy profile of Rh(I)-catalyzed hydrogenation of enamides has been studied for the simple model system [Rh(PH 3 ) 2 (R-acetamidoacrylonitrile)] + using a nonlocal density functional method (B3LYP). Intermediates and transition states along four isomeric pathways for dihydrogen activation have been located, and pathways for interconversion between isomeric reaction pathways have been explored. The general sequence of the catalytic cycle involves coordination of H 2 to [Rh(PH 3 ) 2 (R-acetamidoacrylonitrile)] + to form a five-coordinate molecular H 2 complex, followed by oxidative addition of the coordinated molecular hydrogen to form a dihydride complex, [RhH 2 (PH 3 ) 2 (R-acetamidoacrylonitrile)] + . This dihydride is converted into an alkyl hydride by a migratory insertion reaction. Reductive elimination of the hydrogenated acetamidoacrylonitrile completes the catalytic cycle. No computational support for alternate H 2 activation pathways, such as direct conversion of H 2 and [Rh(PH 3 ) 2 (R-acetamidoacrylonitrile)] + to an alkyl hydride, was found. Four isomeric pathways for hydrogenation are followed, corresponding to the four distinct dihydride isomers resulting from cis addition of H 2 to [Rh(PH 3 ) 2 (R-acetamidoacrylonitrile)] + . Two of these pathways are excluded from further consideration by virtue of their surprisingly high activation barriers for formation of molecular H 2 complexes. Of the two pathways with low barriers to formation of dihydride complexes, only one has a sufficiently low barrier for migratory insertion to contribute significantly to catalytic product formation. Overall, we find that formation of a dihydride is endergonic, rapid, and reversible. Migratory insertion to form an alkyl hydride constitutes the turnover-limiting step in the catalytic cycle. This conclusion is supported by comparison of computed and experimental isotope effects in catalytic enamide hydrogenation.