In studies of Co electrocrystallized on Pt (111) surfaces under electrode potential control, reflection electron microscopy (REM) has revealed a heteroepitaxial and simultaneous multinuclear multilayer growth in the range from 3 or 4 up to about 10 atomic layers. A Co/Pt multilayered structure, as evidenced by the presence of X-ray superlattice diffraction peaks, has been prepared by electrocrystallization, which depends upon the amount of polarization during Co electrocrystallization. The magnetic properties of the electrodeposited Co/Pt multilayers, which tend to exhibit in-plane anisotropy, depend upon the layered structure.