This paper reviews research in the field of automation deciding for assembly systems design. The purpose is to analyze the decision making methodologies already developed in the topic, evaluating previous efforts against practical use by manufacturers in such complex and important decision. Based on this study, a procedure is proposed to support the decision making process regarding the automation throughout the workstations of assembly systems during early conceptual design phase. Requirements for the decision methods are defined. The evaluations and analyzes of existing methods lead to a new decision approach then evaluated against the identified requirements. It is tailored to assist systems designers and decision makers in the determination of the appropriate automation level for their assembly systems.