Mesiodens is atypical supernumerary tooth most frequently found in the upper anterior teeth but it can also be found in the area of the lower incisors. The aim of this study was to estabish the frequency of supernumerary teeth ( mesiodens), their localization in the jaws and the number of mesiodens in children of Knjaževac. The sample comprised 1692 patients of both sexes, 6 -15 years of age, from Knjaževac. 31 patients have mesiodens ( 1,83 %), 26 persons ( 83,87 %) have mesiodens in the upper jaw and only 5 persons ( 16,13 %) have mesiodens in the lower jaw. 28 children have one mesiodens, only three children have two mesiodens. The most frequent site for localization was the area between the upper central incisors.