Aim The aim of this pilot study was to evaluate equations for predicting the size of unerupted canines and premolars during the mixed dentition period in an Iranian population. Methods and Materials This cross-sectional analysis was performed on 106 subjects (52 girls, 54 boys, aged 13–15 years). Data were obtained from dental cast by making direct measurements of the maximum mesiodistal widths of all mandibular and maxillary incisors, canines, premolars, and first molars with an electronic digital sliding caliper, with an accuracy of ±0.02 mm and repeatability of ±0.01 mm. The results were statistically analyzed using Student t tests, Pearson product-moment coefficients, and ANOVA tests. Correlation coefficients (r) and error variance of estimates were determined using a significance level of p<0.05. Results No significant differences were found between the mesiodistal tooth widths of males and females in this Iranian population. The highest correlation was between the sum of the mesiodistal width of canines and premolars in the maxilla with the mesiodistal width of the mandibular first molars and maxillary central incisors (r=0.742). A moderate correlation was obtained in the mandible (r=0.665). Approximations were developed to predict the size of the unerupted canines and premolars in both jaws (in the maxilla, Y = 0.740X + 14.271, or the simplified formula, Y = 3/4X + 14; for the mandibular arch, Y = 0.658X + 16.353, or the simplified formula, Y = 2/3 X + 16). Conclusion The strongest correlation was found for the sum of the mesiodistal width of canines and premolars in the maxilla with the mesiodistal width of the mandibular first molars and maxillary central incisors in the maxillary analysis (r=0.742). A moderate correlation was found in the mandible for the sum of the mesiodistal width of canines and premolars with the mesiodistal width of the mandibular first molars and maxillary central incisors (r=0.665). Clinical Significance The simplified equations proposed for the maxillary arch (Y = 3/4 X + 14) and for the mandibular arch (Y = 2/3 X + 16) offer an easy and practical way to predict the size of unerupted canines and premolars in the maxillary and mandibular arches of Iranian children. Citation Talebi M, Parisay I, Sarraf A, Mazhari F. Regression equations for predicting the size of unerupted canines and premolars in an Iranian population: A pilot study. J Contemp Dent Pract [Internet], 2010 October; 11(5):033-040. Available from http://www.thejcdp.com/journal/view/ volume11-issue5-talebi