Aim: to estimate the age of Egyptian adults using root dentin translucency (RDT)method(Gustafson's morpho-histologic approach). In addition, to compare the accuracy of measuring the surface area versus thelength of RDT in ground section of single rooted teeth in determining the chronological age. Besides, to observethe correlation between RDTand gender.Methods: The study sample was consisting of 50 sound teeth that had been extracted from patient ranging in age from 20 - 70 years then, divided into 5 equal experimental groups. Group I contained sound teeth extracted from patient aged 20-30years.Group IIsound teeth extracted from patientaged 31-40years. Group IIIsound teeth extracted from patient aged 41-50years. Group IVsound teeth extracted from patient aged 51-60years. Group Vsound teeth extracted from patient aged 61-70years. Stained longitudinal ground section for both groups were prepared &observed under light microscope (LM). Both surface area andlength of RDTweremeasured on magnified imagesusing Image-J software. After that, all data were recorded, tabulated, and statistically analyzed using software SPSS.Results:RDT surface area and length was positively correlated with chronological age. The range of difference between chronological and estimated age by both RDT area and length was the lowest (-10.68-8.65) compared to estimated age by RDT area only (-10.89-13.47) and RDT length only (-14.46-16.74).Also, there wasnota significant sex difference determined.Conclusion: RDT is a reliable method for age estimation for permanent sound teeth. we can use specific regression formula for Egyptian population by RDT area, length, or both.