Introduction & Objective: Lack of proper information about the standard dimensions of the male external genitalia will create anxieties and have detrimental effects on the quality of life due to the sensation of matrimonial insufficiency and a wrong estimation of one’s fertility potential. External genitalia size parameters are not the same in different ethnicities and races. Current study is an attempt to establish a standard for the external genitalia sizes in Iranian young men. Correlation between external genital dimensions and sex-related somatometric parameters is also considered.Materials & Methods: We used a multi-staged sampling from different districts of Tehran. The careproviders were taught on how to deal with the volunteers in order to unify the approach. After appropriate application of inclusion/exculsion criteria, 1500 young male volunteers, 20 to 40 years old were recruited. Measurements were obtained for penile length and circumference (glans, and shaft), testicular dimensions and volume, height, weight, waist circumference, hip circumference and index finger length. Penile length was measured only in a stretched-flaccid state. Statistical analyses were performed by SPSS/ SAS softwares and descriptive as well as pearson’s correlation and multi-variate regression tests were utilized.Results: Results for descriptive statistics are: mean age 29.6±5.5 years, mean height 174±6.3 cm, mean weight 78.67±8.4 Kg, mean BMI index 25.8±2.3, mean waist-to-hip (W/H) index 0.91±0.04 and mean index finger length (range) 8.98 ± 0.88 (6.8- 12) cm. Results for penile size parameters (cm) are: mean full-penile length 11.5 ± 1.4 (7.5- 19), (2.5 percentile= 2.5, and 97.5 percentile=14), mean glans length 3±0.3 (2- 4.5), mean girth at mid-shaft 8.6 ± 1 (2.5 percentile=6, and 97.5 percentile=10), mean shaft volume 51.6 cc (±14.5), mean testis volume 21.6 ± 5.6. Multiple regression analysis results: penile and glanular lengths have significant positive correlation with height and index finger length (p<0.001), penile circumference is correlated to hip and index finger length (p<0.001), testicular volume is positively related to age and weight (p<0.001), and negatively related to index finger (p<0.001).Multivariate multiple regression analysis revealed a significant positive correlation between all genital and somatometric parameters with index finger (p<0.002).Conclusions: Standard norms are presented by this study for the male external genital dimensions pending a national study, to act as a reference for the general practitioners and related specialist fields. Also, a correlation of external genital dimensions to other somatometric parameters is substantiated.