In the present study, focus was placed on the ventral arc, which, when used alone, provided 96 percent accuracy in sex determination. This paper stresses the development of the ventral arc in the adolescent: a precursor condition is defined, which first appears at age 14 and becomes the most frequent condition at age 20. In mature adults, four percent show conditions that are misleading and likely to lead to sex determination errors. Practical applications of this method are discussed in relation to the forensic science setting, including three cases. A set of casts was developed to increase the reliability of the method, and these casts were then tested in interobserver error studies. 3 tables, 11 figures, and 5 references (Author abstract)