Background: The value of the mandibulo-canine index (MCI) in gender identification has been proved in some studies in various countries. The goal of our study was to determine the utility of MCI in gender identification in Iran.Methods: This descriptional survey was performed on a group of 18- to 25-year-old Iranian students at the Tehran University of Medical Science. We included 50 males and 50 females that were selected using a single sampling method. Data were statistically analyzed by SPSS (v. 13) and t-test.Results: No statistically significant difference was found between the mean ages of the two groups. Among men, the MCI ranged from 0.209 to 0.293, with a mean of 0.252. Among women, the MCI ranged from 0.202 to 0.276, with a mean of 0.245. There was significant statistical difference between the two means, (0.007; P value = 0.04). The standard MCI of 0.247 was compared to that of each gender, after which no significant statistical difference was found between the two genders (P value = 0.8). Conclusions: Despite some studies performed in other countries displaying the usefulness of MCI in sex determination, our data did not support this conclusion. Perhaps this difference can be explained because of the variety ethnic groups from various cities of Iran represented in this research had some influence on the results.