The applicability of the kink-pair model of solid-solution hardening, initially developed for concentrated alloys with low Peierls potentials by Feltham (1968) to polycrystalline hexagonal alloys is examined with special reference to Ti-Al containing 1-10 at.% of aluminium. The available data on the yield-stress between 77 and 300K are well encompassed by the model; the agreement suggests that the effect of alloying on the resistance to plastic deformation is akin to increasing the Peierls force.