The magnetic properties of a series of electrodeposited [Co (x ML)/Cu (17 ML)](100) multilayers have been examined as a function of the cobalt layer thickness. The multilayers were grown on Si(100) covered with a highly textured Cu(100) seed layer. Films with a cobalt layer thickness less than x < 1.7 monolayer equivalents (ML) exhibit superparamagnetic behavior due to the finite size of the cobalt islands comprising the discontinuous multilayer structure. In contrast, in films with x. 1.7 ML the lateral length scale becomes large enough to stabilize ferromagnetism and the giant magnetoresistance effect is observed. The influence of magnetocrystalline anisotropy is not apparent until 2.5 > x > 3.7 ML. The coercivity increases between 1.6 and 9 ML, reflecting the combined influence of the magnetocrystalline anisotropy and surface roughness.