OBJECTIVE:: To examine the prevalence of oral alterations related to eating disorders and associated factors. METHOD:: A cross-sectional study including 650 adolescents aged from 12 to 16 was carried out through self-report questionnaires (EAT-26; BITE and self-rating hamilton depression questionnaire, SRHDQ) and dental examination. RESULTS:: Significant associations were observed in mucositis, cheilitis, hypertrophy of salivary glands, and dental erosions. The prevalence of adolescents at risk for eating disorders was of 33.1%, according to EAT-26 and 1.7% (high scores) and 36.5% (medium scores), in BITE, higher among 13-year-old females, with brothers, parents or responsible person who are illiterate, being the youngest child, living in a residence of at most two rooms and who showed depressive symptoms. All these factors showed significant relation to eating disorders. DISCUSSION:: Presence of oral alterations is associated to symptoms of eating disorders, helping precocious detection of sub clinical cases. (c) 2009 by Wiley Periodicals, Inc. Int J Eat Disord 2009.