The continuing thrust of organisational research is grounded in an evolutionary field of many perspectives. This paper constitutes the selection of a path through the early conceptualisations of organisations as 'Systems' and the emergent derivatives known as ' Contingency Theories '. The theme of organisational effectiveness' constitutes the goal of the search. The conceptualisation of organisations as systems provides the search territory. The various components of the system represent the paths which research and theory has followed. Issues raised include: What is organisational effectiveness? How may an organisation be described as a system? How are organ isational components, such as structure, people and environment seen from the systems perspective? What would one expect from a manager who employs systems thinking? The contributions of contingency theory are represented as the leading edge of systems thinking, together with some recognition of their problems. To conclude that much is yet to be explored is not to deny that the tools of understanding now available to managers can be of great practical value.