Introduction: Human sacral bones are of great interest to the anatomists, forensic experts and anthropologists as it is one of the important bones used for identification of sex in skeletal remains. Various parameters and indices are available based on which the sex can be determined using sacrum. One such important parameter is the SI. Studies shows that SI significantly varies among male and female gender and among different populations. The calculation of Demarcation Point (DP) of SI increases the accuracy of identification of sex. A review of literature showed that many studies are available in the North Indian population whereas there is a dearth of information about the normal SI and DP in South Indian population particularly in the Tamil Nadu and Andhra Pradesh, Inida region. Therefore, the present study aims to create a database for the SI in the above mentioned population. Material and Methods: 123 bones of known sex (63 males and 60 females) belonging to Tamil Nadu and Andhra Pradesh, India region were studied. Bones with obvious pathology were excluded. The breadth and length of the sacra were measured using vernier calipers based on standard guidelines. The SI and DP were calculated. The statistical analysis was done using SPSS 15.0 package. Results: The mean SI for male and female sacra were found to be 96.32 + 5.40 and 102.92 + 4.00 respectively. The Demarcating Point was found to be < 90.29 in males and > 112.43 in females. The mean length of male and female sacra was 97.8 mm and 90.6mm respectively. The mean width was 93.7mm and 92.91 mm respectively for males and females. Conclusion: The average SI and DP identified in the present study would be of use to the anatomists, forensic experts and