This paper introduces and critiques key contributions of Contentious Politics, a booming subfield in comparative political sociology, representing the culmination of epistemological ferment set in motion in the late 60s. Rather than seeking the ultimate causes of social protest (as if it were an aberration), contentious politics focuses instead on its mechanisms and modalities. This has involved analysing environments conducive to mobilisation; collective action repertoires; the discourse claimants formulate to advance their demands; organisations and mobilising structures. Queries and antinomies, however, remain. The paper focuses on five: (a) How to adjudicate between reasonable but mutually incompatible definitions of ‘social movement’? (b) Given that contentious politics is a ‘partial theory’, how does it relate (if at all) to Grand theory? (c) Is activism incompatible with scholarship or is it a prerequisite? (d) Do social movements reflect utilitarian calculi or are they the product of cultural-expressive impulses? Finally, (e) Structure or Action?