This chapter describes the various theoretical approaches to organizational design. Complexity of the organization is a significant driver of organizational design, and a major aspect of this is the size of the organization. Size does not always imply complexity but it often does and, in any case, complex or not, size of the organization has clear implications for design and structure. Taylor and Fayol felt that the most efficient and effective organizations had a hierarchical structure based on a legalized, formal authority. Think of organizations as ranging from simple to complex and from static to dynamic. Complexity and dynamism tend to imply a greater need for flexibility, adaptability and an organic feel to the structure. The members of the organization were guided by a sense of duty to the organization and by a set of rational rules and regulations. Another contingency or circumstance or factor that has a significant influence on organizational design and structure is technology.