INTRODUCTION To achieve proper occlusion, practitioners must consider tooth-size discrepancies between the jaws. Previous studies have shown considerable differences in tooth sizes between sexes, ethnicities, and malocclusion categories. The aim of this study was to compare mean tooth-size statistics between these groups, specifically determining a maxillary or a mandibular excess tooth-size discrepancy in clinically relevant cases. METHODS This study involved 306 subjects of varying sex, ethnicity, and malocclusion category, randomly chosen from the treatment population of the orthodontic clinic at the New Jersey Dental School, University of Medicine and Dentistry of New Jersey. The prevalence of discrepancies (±1 and 2 SD) between all groups and within groups was measured. RESULTS Fifty percent of the subjects had anterior Bolton tooth-size discrepancies, and 41% had overall Bolton tooth-size discrepancies of ±1 SD. Tooth-size ratios compared with analysis of variance (ANOVA) showed no significant correlation between and among the sexes, ethnicities, and malocclusion groups. Compared with Caucasian and Hispanic patients, African-American patients had significantly greater odds of having a clinically significant (±2 SD) anterior ratio. When we compared the numbers of subjects above or below the clinically significant ratio, there was equal distribution of maxillary and mandibular excess in Class II and Class III patients. Caucasian and African-American patients had equal distributions of maxillary and mandibular excess, whereas Hispanic patients displayed a higher bias toward mandibular excess. CONCLUSIONS Tooth-size discrepancies are common in orthodontic populations and are evenly distributed among sex, ethnicity, and malocclusion category, with some exceptions.