Affordance is a fundamental concept in the ecological approach to perception and action, but it is not yet fully developed. In this article, I attempt to further the development of the concept by contrasting it with the concept of events. My specific purpose is to raise for further discussion the following question: Can a theory that predicts the perception of affordances also predict the perception of events? I argue that affordances and events are not identical and that they differ qualitatively. I also discuss what I call mutuality relations between the animal and its environment, which have inspired much research on perception-action couplings (e.g., the perception and control of interceptive action, or the guidance of locomotion). There has been little direct discussion of relations between perception-action coupling and affordances. I suggest that mutuality relations are not affordances and that they may be a category of events. As an example of this argument, I reinterpret common analyses of time-to-contact in terms of affordances for interceptive action. I argue that the utility of affordance perception is clear but that it is uncertain how an ecological theory could predict the perception of events. I conclude with a brief discussion of some additional issues that remain to be resolved in the concept of affordances.