Abstract: The binding energies of transition metal clusters have been measured as functions of cluster size and composition at first time. The following clusters have been studied. They are cobalt, niobium, iron, nickel, vanadium, tantalum and palladium with cluster size up to 20 atoms. The photodissociation measurement showed that the binding energy is roughly constant with different cluster sizes but differs with different cluster compositions. For almost all clusters measured, the primary one-photon fragmentation pathway is always found to be loss of a single metal from the cluster.