All current standardized methods of age determination using the os pubis were tested by blind assessment of a skeletal sample with documented ages (from the Todd collection; N = 96). No demographic data (sex, age, race, age composition) were known to the assessors prior to completion of the test. Results showed the Todd method to be more reliable than more recent component techniques and that all systems tended to underage. Therefore, modifications were made of the Todd system to eliminate this and other deficiencies, and a second test using a new sample was conducted (N = 109). The age distribution determined by the revised Todd method did not significantly differ from the actual age distribution of the second sample. Error due to race was nonsignificant. Biological stages of pubic metamorphosis are described and possible evolutionary specializations of the hominid symphysis are discussed. Revised standards for age determination are presented.