This study explores the dynamic relations between cultural forms and political formations in some urban cultural movements. The analysis is based on a detailed study of the structure and development of the London Notting Hill Carnival, widely described as Europe's biggest street festival. Started in 1966 as a small-scale, multi-ethnic local festival, it grew into a massive West-Indian dominated affair that over the years occasioned violent confrontations between black youth and the police. The carnival developed and mobilized a homogenous and communal West-Indian culture that helped in the struggle against rampant racism. The celebration is contrasted with other carnival movements, such as California's `Renaissance Pleasure Faire'. Analytically, this is a follow-up to Cohen's earlier studies of the relations between drama and politics in some urban religious, ethnic and elitist movements in Africa. The conclusion focuses on the processes underlying the transformation of rational political strategies into non-rational cultural forms.