This paper reports an empirical study on assessment of R&D best practices. The principles of quality management and their tools such as best practices or benchmarking have been so prevailing in the operational process that the R&D management recently consider extensive use of them for their innovation process. However, characteristics of the two processes may be different each other. Are the principles or the tools that were effective in the operational field still going to be effective in the innovative field? In order to answer the question, we statistically examine how R&D best practices contribute to the innovative performance. Upon literature review on technological innovation, we present a R&D process model whereby we set forth research hypotheses. Using data from 66 successful R&D efforts carried out among Korean firms mostly between 1999-2001, regression analyses reveal that best practices used in most stages throughout the R&D process are found not to significantly contribute to the innovative performance. Only those in technology strategy and prototyping stages are proven effective for technical and commercial performance respectively. Interestingly, efforts in a problem solving and improvement stage are counterproductive in the case of the innovation process. Discussions on our empirical observations are presented followed by some managerial implications.