Using a panel data on Taiwanese manufacturing firms from 1990-1997, this study investigates the relationship among technological knowledge, spillover and productivity. In addition to R&D stock, we also employ patent counts to construct the output-side indicators of knowledge and spillover to explore the relationship between knowledge and productivity. We find a very significant contribution of R&D, patents and spillover stock to productivity. In addition, the magnitude of the patent stock coefficient is substantially larger than that estimated by R&D stock. Our results imply that innovative activity investment has been very productive in increasing output for Taiwanese manufacturing firms in the 1990s.