The micro-level of administrative processes is in essence a set of interlocked roles and routines. Generally, such processes are viewed as neutral instruments and also of trivial importance. Contrary to such a view, this dissertation argues that at the micro-level, roles and routines, far from being simple and clear, turn out to be complex and ambiguous. This is because their interaction involves different institutional rules, agency norms, information, and cognitive orientations that need to be continuously accommodated in a seamless web of implementation. The creation and retention of ambiguity is conceived of as a natural outcome of such accommodation. This dissertation explores such a possibility in the role-routine interactions involved in the execution phase of the budget process. Budget execution is widely held to be a control process. But the nature of such control is far less straight-forward and far more complex than is commonly assumed. The dissertation explains the management of such complexity in terms of the retention of ambiguity in the control processes of budget execution.