Drawing on Wilson, we identify four types of police agencies by cross-classifying levels of bureaucratization with professionalism. Evidence from the analysis indicates that factors influencing arrest decisions are conditional on the organizational contexts in which such decisions occur. In different types of police agencies, officers respond to similar situations differently. Hence, 'global' decision-making models are more incomplete than incorrect. We argue that consideration of the contexts within which discretion is exercised is necessary for advancing our understanding of decision-making in justice system agencies. (Publisher abstract)