The research goal is to advance the state of the art in the design of planar and spatial mechanisms, with particular focus on kinematic and dynamic accuracy performance. Four topics will be investigated. In the first topic, kinematic synthesis for closed chain mechanisms, the relationship between the sensitivity to variations of link lengths and the location of the moving pivots of four link, six link and other complex mechanisms will be investigated for the objective of three and four position synthesis. The second topic, kinematic synthesis for three dimensional open chain mechanisms, looks at design guidelines for optimizing mechanism endpoint accuracy performance. In the third topic, dynamic synthesis for open chain multi axis mechanical systems, a new way of modeling three dimensional dynamic error as a function of frequency domain transfer function gain and delay time variations between axes is developed. The fourth and last research topic develops computer simulation tools for identifying spatial accuracy of open chain mechanisms. The overall research results are expected to be useful for practicing engineers in optimizing designs of planar and spatial mechanisms early in the design process. Traditionally, design for performance has been subordinated to the design for strength and design for manufacturing functions. This research attempts to compensate for that reduced emphasis.