In this study, microstructure and mechanical properties and electrical conductivities of in situ Cu-Fe-Xi(Xi=Ag, Cr or Co) alloy wires obtained by cold drawing combined with intermediate heat treatments have investigated. During cold working the primary and secondary dendrite arms are aligned along the drawing direction and elongated into filaments after deformation processing. The addition of Ag was found to be more effective in reducing the microstructural scale at the given draw ratio than that of Co or Cr throughout the drawing processing. The ultimate tensile strength and the conductivity of the Cu-Fe based composites containing Ag were higher than those of Cu-Fe composites containing Co or Cr. The good mechanical and electrical properties of Cu-Fe-Ag wires may be associated with the more uniform distribution of the finer filaments in the wires containing silver. The strength of Cu-Fe-Xi composites is dependent on the spacing of the Fe filaments in accord with a Hall-Petch relationship. The fracture surfaces of all the specimens showed ductile-type fracture and iron filaments occasionally observed on the fracture surfaces.