Accident theory is foundational for all aspects of OHS management. Models are examined, drawing on disciplines such as psychology, epidemiology, engineering, ergonomics and organizational studies. Of particular importance is the distinction between root causes and behavioural causes. The importance of accounting for all possible categories of losses is emphasized. The aim is not to provide the "one best" model, but to analyze the strengths and weaknesses of each model and to assess their usefulness for various purposes.