Cancers of the head and neck have always represented a unique perspective in cancer staging. Not only are these lesions numerous in terms of anatomic sites of origin, but, unlike most other major cancers, they frequently and readily lend themselves to adequate clinical assessment by visual inspection and palpation, which greatly facilitates documentation by the trained clinician. In addition, their location often involves treatment programs that focus on nonsurgical organ-preservation strategies, and thus anatomic and histological data for comprehensive pathologic staging are often not available. Nevertheless, the processes involved in surgical decision-making and radiotherapy treatment planning require meticulous assessment and documentation of the extent of locoregional disease. For all these reasons it is especially important to perform reliable and accurate pretreatment clinical staging of head and neck cancers. Also, many patients who succumb to head and neck cancer do so as a result of locoregional disease. Therefore, the staging system must take into account detailed local anatomic features that dictate management, since the degree of involvement of these structures by tumor may be as important as distant metastasis in threatening survival. For this reason the most recent cancer staging classification (6th edition) of the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC) includes new criteria for the more advanced cases (e.g., T4 categories and stage IV disease). These criteria reflect the fact that in heterogeneous populations there is a realistic opportunity for cure in some patients but not in others. This review summarizes the criteria used in the new TNM for head and neck tumors, and outlines the rationale behind the current changes. It also provides some guidance regarding optimal source data to facilitate classification in the registry setting. In addition, the need for additional changes in the future is recognized.