objectivethis study was aimed at determining dental fluorosis prevalence and severity amongst 6-13-year-old students residing in medellin, colombia. methods a descriptive study was carried out on 1,330 students attending 34 public schools in the city of medellin. two dentists trained in dental fluorosis diagnosis performed the examinations were after the teeth had been brushed. teeth were dried with gauze, isolated with cotton pellets and visually examined in natural light. the thylstrup and fejerskov index (tfi) was used for rating fluorosis. results dental fluorosis prevalence was 81 % (tfi>1); 46.4 % was related to mild dental fluorosis (tfi1 and tfi2) and 8.8% to severe dental fluorosis (tfi >5). tfi>=1 was found in 21 % of the children being examined in at least 50 % of their teeth. conclusion dental fluorosis prevalence level was found to be high in medellín, colombia; health authorities should thus focus their attention on preventing this problem.