The structure of magnetron-sputtered Ni80Co20/Cu multilayershas been investigated by low and high-angle X-ray diffractometry. Low-angle x-ray reflectivity data reveal well-defined compositional modulation along the film growth direction for a wide Cii thickness range of 5-40 Å. The data analysis, based on anl optical model, shows that interfacial mixing is limited to ∼3-4 Å As the number of bilayers increased from 8 to 100, the interface roughness increased by a factor of 3. Better layered structures were found for relatively thick Cu layers (tCu>10Å). The high-angle diffraction data were analyzed using a trapezoidal model. The results indicate that the films have a polycrystalline structure with a preferred (111)orientation with coherent interfaces of ∼ 100-240 Ådepending on the Cu layer thickness. The relatively large expansion of (111) spacings in NiCo alloy layers gives rise to the lower atomic ordering in NiCo/Cu multilayers.