Sandia National Laboratories is a vertically multi-disciplined research and development laboratory with a long history of designing and developing sophisticated electro-mechanical products in the national interest. Integrating new technologies into the prototyping phase of our development cycle is necessary to reduce the cycle time from initial design to finished product. The introduction of rapid prototyping machines into the marketplace promises to revolutionize the process of producing prototype parts with relative speed and production-like quality. Issues of accuracy, feature definition, and surface finish continue to drive research and development of these processes. Sandia uses Stereolithography (SL) and Selective Laser Sintering (SLS) capabilities to support internal product development efforts. The primary use of SL and SLS is to produce patterns for investment casting in support of a Sandia managed program called FASTCAST that integrates computational technologies and experimental data into the investment casting process. These processes are also used in the design iteration process to produce proof-of-concept models, hands-on models for design reviews, fit-cheek models, visual aids for manufacturing, and functional parts in assemblies. This presentation will provide an overview of the SL and SLS processes and an update of our experience and success in integrating these technologies into the product development cycle. Also presented will be several examples of prototype parts manufactured using SL and SLS with a focus on application, accuracy, surface finish, and feature definition.