Abstract: This paper explores the case theory and its development in the principles and parameters framework, providing evidence that the distinction between structural case and inherent case as well as case assignment poses serious conceptual problems.It is argued that not every DP has to pass the Case Filter as defined by Chomsky and that the Case Filter should be based on the co-existence of the case assigner and the case assignee.The Case Filter is redefined as a set of conditions: i)A case assigner must be accompanied by a case assignee which checks its case feature; ii)A case assigner must locally c-command its case assignee; iii)A potential case assignee (i.e., DP) is exempt from the Case Filter and bears the default case when there is no case assigner; iv)Of two potential case assignees, the one with morphological case marking must pass the Case Filter when there is a corresponding case assigner.Case is realized on the head of DP and the case of DPinternal nominal constituents is determined parametrically.