Background: There has long been an understanding that a certain maxillary –to-mandibular tooth size relationship is important for proper occlusal relationships. The purposes of this study were to compare the Bolton ratio’s (Anterior and total) of skeletal and dental Cl I individuals in Shiraz and to assess the sizes of teeth and correlation coefficient between similar teeth in the left and right sides and in the upper and lower jaws in males and females.Materials and Method: The data were derived from collected post treatment casts of 50 class I skeletal and dental patients (29 females, 2 1males) treated orthodontically by none-extraction method. Measurements of the mesio-distal size (M-D) were performed on the models and Bolton ratios were calculated. Then statistical analysis was done to compare the tooth size and also Bolton ratios.Results: The teeth size correlation was calculated 0.9 between the right and left sides of the jaws and 0.8 between the similar teeth in the upper and lower jaws. The mean value and standard deviation (SD) for the anterior and total ratios were: %77.2 + 2.66, %90.6 + 2, whit no significant difference with Bolton’s ratios, but the range of ratios was greater respectively in our sample. The ratios were also compared among males and females, but no sex dimorphism was seen.Conclusion: 1- The upper maxillary incisors had the most variable M-D sizes. 2- There was no sex difference in the M-D tooth size of this sample. 3- Although the values of ratios were not significantly different from those of Bolton’s value, the greater range and SD of the ratios showed the different distribution patterns of the ratios in our study. Therefore a careful analysis of interarch relationship should always be induced in diagnostic procedures.Key words: Bolton analysis, Ant ratio, Total ratio