Parliaments qualify as complex organizations. Work staff is vital. Parliament is no exception. The use of parliamentary staffs reflects an effort to acquire institutional expertise and professionalism in the legislative branch to counterbalance a perceived advantage within executive agencies. There are different models of parliament and administration. Mixed models may emerge over time. Parliamentary staffs represent a thread of continuity, institutional memory, and expertise within the institution and constitute something more than just an occupational grouping and something less than a fully established profession even if they are professionals in pursuit of political outcomes. Staff have specialized expertise, substantial and qualified autonomy, commitment to political enterprise and public service, and identify themselves as a professional group. Historically within Italian parliamentary administration institutional forces influenced strategic and organizational changes that have affected the professional development of staff consistently with transition from registration to consulting staff structure. Professionalism and expertise within parliamentary staff may develop and increase in relation to different degrees of organizational complexity.