The authors use confidential interviews with Supreme Court justices, analysis of their rulings from 1970 to 2005, and measures that tap their perceived ideological tendencies to provide a critical examination of the ideological roots of judicial decision making, uncovering the complexity of contemporary judicial behaviour. Examining judicial behaviour through the lens of three different research strategies grounded in qualitative and quantitative methodologies, Law, Ideology, and Collegiality presents compelling evidence that political ideology is a key factor in decision making and a prominent source of conflict in the Supreme Court of Canada.