 Assessment of oral and dental problems is seldom routine in clinical oncology, despite the potential negative impact of these problems on nutritional status, social function and quality of life QoL. A brief, assessment tool for oraldental health and related QoL-issues to improve symptom management has been requested. The present study will be conducted on behalf of and with support from the European Organisation for Research and Treatment of Cancer - EORTC Quality of Life Group QLG. The study represents phase IV, the final step, in the development of an international, symptom specific questionnaire module, focusing on oral and dental problems in relation to cancer and its treatment. Phase I-III of this stepwise development process was conducted from 2008 to 2011, as an international collaboration and conducted according to the guidelines for module development set forth by the EORTC QLG. The resulting module, the QLQ-OH17, is now subject to an international field testing and validation study as described in this project description. 