Several approaches have emerged for understanding how policy advisory systems are organised and operate. A dominant early theme in PAS research has been location, focusing on distributional issues about where the supply of advice was located and the ability of a government to control it. Research charted the ascendency and decline of advisory units, with an emphasis on the public service’s changing role, and the impacts on policymaking and governing of new sources of supply and shifting demand. A second approach has been the content of policy advice. This has recognised that, while location was important, the composition, operation, and influence of units within these systems were in part a result of the congruence of the content of advice with demand, regardless of the location or government control. Third are the dynamics linked to the stability and change of individual components or entire systems over time. The main focus has been the externalisation and politicisation of these systems because of their significance and identifiability. Another approach is to examine change according to its magnitude: from overarching frameworks to micro adjustments. Finally, organisational dynamics are considered as types of advisory units rise and fall in significance or change character.