This paper presents a CMOS gate-array version of Digital System Design Language/Synthesis eXpert (DDL/SX), a rule-based system for logic circuit synthesis. The system inputs technology-independent functional diagrams, and automatically generates conventional technology-dependent logic diagrams in order to eliminate time-consuming and error-prone tasks in logic design. Because the synthesis process was not clear enough to establish a fixed algorithm, a rule-based approach was adopted to develop the system. This approach made it easy to incrementally improve the system's capabilities by adding, modifying, or deleting design knowledge represented as rules. Experimental use of the system revealed that the automatically generated logic design is almost as good as a manual design, and the design time is reduced by a factor of four.