It has been argued that nonreductive physicalism leads to epiphenominalism about mental properties: the view that mental events cannot cause behavioral effects by virtue of their mental properties. Recently, attempts have been made to develop accounts of causal relevance for irreducible properties to show that mental properties need not be epiphenomenal. In this paper, I primarily discuss the account of Frank Jackson and Philip Pettit. I show how it can be developed to meet several obvious objections and to capture our intuitive conception of degrees of causal relevance. However, I argue that the account requires large-scale miraculous coincidence for there to be causally relevant mental properties. I also argue that the same problem arises for two apparently very different accounts of causal relevance. I suggest that this result does not show that these accounts, on appropriate readings, are false. Therefore, I tentatively conclude that we have reason to believe that irreducible mental properties are causally irrelevant. Moreover, given that there is at leastprima facie evidence that mental properties can be causally relevant, my conclusion casts doubt on nonreductive physicalist theories of mental properties.