This article asks four questions: (1) What are our theoretical expectations about the incidence of policy-oriented collective action and its impact?(2) What do the data show about the incidence of collective action and its impact? (3) How might the impact of collective action be related to its incidence? (4) What do our findings imply for our understanding of democratic politics? We suggest that predictions that little collective action will occur are more accurate than conventionally believed; that such action is often ineffective; that it may be ineffective partly because it is so infrequent; and that the analysis of the determinants of policy change should be rethought as a result.