The objective of this study was to investigate the impact of fluorosis on the size of deciduous and permanent teeth, and to compare the data with those of teeth without fluorosis. Plaster molds were obtained from 180 patients between the ages of 8 and 16 (mean 11.9 +/- 0.4 years) who were eligible for the study. The molds were divided into deciduous and permanent teeth according to the ages of the patients, and teeth were divided into five groups according to the level of fluorosis. No significant differences were found in the dimensions of deciduous teeth between all groups (p>0.05), even in patients with late mixed dentition. However, for the permanent teeth, the dimensions were generally lower in the fluorosed teeth than in the nonfluorosed healthy teeth. These differences were found between mesio-distal dimensions of permanent maxillary, right, and left central incisors, respectively (p = 0.010 and p = 0.012), and between left second premolars (p = 0.035) and left first molars (p = 0.043). For the mesio-distal dimensions of mandibulary teeth, a significant difference in dimensions of first molars (p = 0.018) and in left central incisors (p = 0.002) was found.