The influence of a small amount of silicon (up to 6 at %) on the structure and microstructure of rapidly solidified equiatomic TiNi alloys is reported. It is shown that a small amount of silicon suppresses the B2 TiNi formation and promotes a competitive nucleation of Ti2Ni phase. Further additions of silicon promote the formation of glass. The behaviour of the ternary replacement of both titanium and nickel by silicon has been studied. It is shown that replacement of titanium increases the tendency for the formation of silicide phases while the latter is absent when silicon replaces the nickel atoms.