The aim was to produce evidence-based guidelines on mouth care for children, teenagers and young adults receiving chemotherapy and/or radiotherapy. Systematic reviews were undertaken and research was graded according to the methods of the Scottish Intercollegiate Guidelines Network. Where no relevant research was identified, an opinion-gathering process was undertaken. ‘Best practice’ recommendations were developed with regard to appropriate dental care and basic oral hygiene. An evaluation of oral assessment tools identified seven which had been assessed for reliability and/or validity. Only Eilers’ Oral Assessment Guide was felt to be relevant for daily clinical practice. A variety of interventions have been used for the management of oral mucositis, candidiasis, xerostomia and herpes simplex virus; few are supported by research evidence. Careful oral management of children treated for cancer can improve the quality of life during treatment. The guidelines have the potential to improve patient care by promoting interventions of proven benefit and discouraging use of ineffective or potentially harmful practices which may result in adverse patient outcomes.