This paper estimates the effects of inter-industry R & D spillovers on the production cost of nine major Canadian industries. Production costs in all nine are affected by spillovers and six industries are influenced by at least two different source industries. Rates of return to R & D capital for each industry are also estimated. Private rates of return on R & D are at least two and a half times those on physical capital. Rates of return on R & D, inclusive of spillovers, are also computed: for industries which are major sources of spillover the spillover-inclusive returns are at least twice the private returns.