Policy advisory systems" have been central to moving beyond individual actor considerations to assessments of the interactive effects of multiple interlocking sets of suppliers, in specific jurisdictions, that provide policy advice to policymakers. This article argues, while useful, the advisory system concept should be revised given that previous approaches animated by the location of supply and government control over it have been weakened. We argue for a "second wave" of advisory system studies that: (1) reorients the unit of analysis from the public service to advisory systems themselves, (2) better contextualizes advisory system operation and dynamics based on the subsystems within which they operate, and (3) focuses on questions of why advisory system components combine in particular policy instances and with what effect. Using access and compatibility, we posit a typology of policy advisory networks and develop four archetypes of policy ideational compatibility. KEY WORDS: policy advice, policy theory, public management, subsystems, context 215 0190-292X V C 2015 Policy Studies Organization