The codification efforts are the American Law Institute's Model Penal Code, the Law Reform Commission of Canada's 1986 report entitled "Recodifying Criminal Law," and the British Law Commission's 1989 Draft Criminal Code Bill. Defining a voluntary act requires the specification of the necessary attributes of a human action without which a person may not be held accountable for the harm that ensues from it. Liability for failure to act concerns the definition of circumstances that render a person accountable for a harm resulting from an avoidable omission. Mens rea provisions must define the mental states accompanying an action, from deliberate intent to unavoidable accident, that determine the extent to which actions are culpable. The law of complicity determines the kinds of actions and intentions that render a person liable for a crime committed by another. How these issues are handled in the three codification efforts is considered in this article. 23 footnotes