A comprehensive theory of agency will encompass not just acting but also omitting to act and refraining from acting. Some theorists maintain that a causal theory can be applied to acting, omitting, and refraining in a perfectly uniform manner, for each omission or instance of refraining can be identified with some garden-variety action. Here it is argued that in plenty of cases this strategy fails. Sufficient conditions for omitting or refraining are offered that do not require there to be, in every case, anything that is an omission or act of refraining. Disjoining these with a causal theory of action would leave us with a view of agency that is less uniform than what might have been preferred; but diversity in the subject matter, it is suggested, might preclude any more uniform theory.