The objectives of this study were to investigate the tooth size discrepancies in Malaysian orthodontic population. Ninety preorthodontic dental casts from samples of Malays (n= 30), Chinese (n= 30) and Indians (n = 30) in University of Malaya were used in this study. Mesiodistal widths, measured from the contact points of canine to canine for anterior ratio and first molar to first molar for overall ratio were measured on each cast to the nearest 0.01mm, by using digital callipers (Pro-Max Callipers) links to Hamilton Arch Tooth System software. Anterior and overall ratios were calculated using Bolton analysis. One way ANOVA was used to analyse comparison between ethnics of the anterior ratio and the overall ratio with the level of statistical significant set at p<0.05. The mean values of anterior ratio and overall ratio for Malays are (78.93 ± 2.67%), (92.51 ± 2.21%) showing the highest ratio mean, with the lowest anterior and overall ratio displayed by Chinese at (76.55 ± 2.68%), (90.93 ± 1.87%), and Indians at (77.77 ± 2.89%), (91.37 ± 2.26%) respectively. The ANOVA test is significant for anterior ratio (p=0.005) and overall ratio (p=0.015). Subsequent post hoc test with Bonferroni procedure shows that there are significant different (p<0.05) found between Malays and Chinese of the anterior ratio (p=0.004) and overall ratio (p=0.015). In conclusions, the findings of the study can be used as a norm value in treatment planning for each ethnic. Significant differences in the ratios between Malays and Chinese suggest that population specific standards are necessary for clinical assessments.