This investigation was undertaken to compare the mesio-distal crown dimensions of the permanent teeth in subjects with and without fluorosis. For this study, 25 pairs of study models cast immediately from alginate impressions of children from each of the two groups were evaluated. Their mean ages were 13.9 +/- 1.6 and 13.9 +/- 1.4 years, respectively. A dental vernier calliper was used to record the maximum mesio-distal dimensions. Analysis of the study models showed that there were no statistically significant differences between the left and right sides (P > 0.05). The results indicated that the mesio-distal crown diameters were consistently larger in the subjects with non-fluorotic permanent teeth. With the exception of the mandibular first premolars, there were no statistically significant differences in the mesio-distal crown diameters of the two groups.