A systematic study of Al/metal reactions has been performed. The thin-film interactions of Al with refractory metals (Ti, V, Ta, Cr, Mo, W and Co) and near-noble metals (Ni, Pd, and Pt) have been investigated. The initial aluminide phases to grow are the Al-rich phases: TiAl3, Val3, TaAl3, Cr2Al13, MoAl12, Wal12, Co2Al9, NiAl3, Pd2Al3, and Pt2Al3 at temperatures between 225 and 525°C. With the exceptions of Val3, Pd2Al3, and Pt2Al3. these are the most Al-rich phases on the phase diagrams. Marker experiments were performed and Al was the dominant diffusing species during the growth of these phases, TiAl3, Val3, Cr2Al3, MoAl12, Co2Al2, NiAl3, Pd2Al3, and Pt2AI3. Consistent with the faster Al diffusion, which provides a greater supply of Al to the growing interface, is the growth of the most Al-rich phase initially. For the exceptions to this rule, Val3, Pd2AI3, and Pt2 Al3, the complexity of the Al-rich V, Pd, and Pt end phases may have hindered nucleation, resulting in the growth of the observed phases. The subsequent phase formation was examined in the Ni-, Pd-, and Pt-Al systems. After initial phase formation consumed all the Al or metal, subsequent phases formed in accordance with the overall stoichiometry. The results of this study, along with a brief literature review, are presented and the generalized behavior of Al/transition metal reactions discussed.