Co-59 NMR and magnetotransport measurements have been undertaken on a series of molecular beam epitaxy grown Co 22 Angstrom/Cu 32 Angstrom(111) multilayers as a function of the number of repeat units in the multilayer stack. Examining the positions of the bulk [Co surrounded by 12 Co nearest neighbors (NN)] and ideal planar interface (Co surrounded by 9XCo and 3XCu NN) lines showed that increasing the number of repeat units leads to greater strain in the Co layers indicating better epitaxial registry. Interfacial mixing was studied by examining the ratio of the relative signal strength of the bulk and ideal planar interface lines compared to the signal outside these regions. The relative intensity of the NMR signal outside the bulk and ideal interface lines clearly reduces as the number of repeat units is increased. This demonstrates that in these samples the interfacial quality improves as the number of repeat units is increased. Magnetotransport measurements show that the improvement in structural quality could be correlated with an increase in magnetoresistance Delta R/R. (C) 1997 American Institute of Physics.