Magnetoresistance of a permalloy monolayer and NiFe(t)/Cu(s)/NiFe(t) multilayers has been investigated in correlation with their microstructural properties. The thickness, t, of NiFe layers ranged from 4 to 12 mm, while that of the copper layer, s, was ranged from 3 to 8 nm. The multilayers exhibit magnetic properties different from those found in a single NiFe film, such as the giant magnetoresistance effect (GMR). By decreasing the NiFe layer thickness and increasing the Cu layer thickness, the influence of interface intermixing effects on magnetic properties becomes more important. The GMR effect is influenced by the grain size of the NiFe layer.