This second monograph in the Mechanical Design Engineering Series deals with the subject of Design for Assembly. It consists of five chapters whose content descriptions follow. Chapter-1 deals with the importance of DFA, an operational definition of assembly, part characterization, reasons for separate parts and creating a apart sequence diagram. Chapter-2 presents and discusses with examples generally accepted DFA product development guidelines. These include: providing a base for assembly, layering and stacking, using multi-functional parts, accommodating for errors, reducing fasteners, limiting flexible items and minimizing part count. Chapter-3 discusses the design of parts to facilitate their feeding and insertion. Topics include the avoidance of tangling, overlapping and nesting, the role of gravity, the value of geometric symmetry and the use of asymmetry. Chapter-4 presents a four-step process for applying DFA principles to the improvement of existing products. A number of examples of the process application are included and discussed in detail. Chapter-5 introduces a technique that numerically quantifies the ease of assembly based on the feeding, insertion and fastening of parts. It is used to quantitatively compare the degree of improvement that DFA can make in a number of product examples.