The effects of two additives, sudium dodecyl sulfate (SDS) and saccharin, on the composition and microstructure of pulse-plated Cu-Co alloys have been studied. The additive SDS appears to promote the displacement of Co by Cu during pulse off-times in the pulsed deposition of Cu-Co alloys. For short pulse periods, films made with SDS only are composed of Go-rich columns surrounded by a Cu-rich matrix phase. Films made with both SDS and saccharin at short pulse periods are face-centered cubic in orientation with a grain size of about 10-15 nm. The interfacial planarity of laminated Films produced at longer pulse periods is improved by saccharin. By taking advantage of the self-organizing Go-rich columns obtained at short pulse periods and using Cu spacer layers, it is possible to obtain three-dimensional arrays of Go-rich nanophases using a single electrolyte and no masking of lithographic processes.