Five basic measurements of the male external genitalia were studied in 320 healthy male medical students belonging to the various parts of Nigeria (West Africa). Their ages range from 17 to 23 years. The measurements were as follows: average length of the penis (81.6 +/- 0.94 mm); circumference of the penis (88.3 +/- 0.02 mm); circumference of the scrotum (212.6 +/- 2.48 mm); length of right testis (46.8 +/- 0.54 mm); width of right testis (32.4 +/- 0.37 mm); length of left testis (46.0 +/- 0.53 mm); and width of left testis (31.4 +/- 0.36 mm). The size of the genitalia increases with the increase in age in younger year groups. The adult stages of genitalia development are reached at the age of 21 years in 89.0% of the individuals. The growth of the genitalia is continued with the increasing height and weight, but this growth slows down after attaining a definite height and weight.