This chapter deals with automation of machining lines, sometimes called transfer lines, which are serial machining systems dedicated to the production of large series. They are composed of a set of workstations and an automatic handling system. Each workstation carries out one identical set of operations every cycle time. The design of transfer lines is comprised of several steps: product analysis, process planning, line configuration, transport system design, and line implementation. In this chapter, we deal with line configuration. Its design performance is crucial for companies to compete in the market. The main problem at this step is to assign the operations necessary to manufacture a product to different workstations while respecting all constraints (i.e., the line balancing problem). The aim is to minimize the cost of this line while ensuring a desired production rate. After a review of the existing types of automated machining lines, an illustration of a developed methodology for line configuration is given using an industrial case study of a flexible and reconfigurable transfer line.