This paper describes the implementation of a prototype expert system that provides standard cell design advice in the areas of performance, manufacturability, testability, and overall design quality, from a netlist description of an application specific integrated circuit (ASIC) design.The system is currently being developed on a Symbolics Lisp Machine using a hybrid AI programming language, called Proteus. The language integrates both known and novel AI programming techniques into a robust vehicle for the implementation of knowledge-based systems.Knowledge representation schemes, inference mechanisms, and knowledge acquisition techniques will be presented, including representative examples from within the knowledge base.