The structural, magnetic and magnetoresistance properties of Co/Ag multilayer films prepared by thermal coevaporation were studied. When the Ag layer was $60{AA}$ thick, the Co layer behaved ferromagnetically even with the thickness of $5{AA}$. However, when the thickness of Ag layer was $30{AA}$ and that of Co layer was less than $15{AA}$ thick, the Co layer became discontinuous and the islands of Co behaved mostly superpararnagnetically. The maximum MR ratio, 6.1% was obtained in the $3000{AA};Ag30{AA}/Co10{AA}$ Ag30 A ICo 10 A discontinuous multilayer. Agglomeration of the Co layer was promoted by annealing and hence MR ratio increased when the thickness of Ag layer was thinner than $15{AA}$. The SiO underlayer enhanced the MR ratio in the $1000{AA}$ thick multilayer via the layer structure improvement.