High Quality Content by WIKIPEDIA articles! The Selective Service System is a means by which the United States government maintains information on those potentially subject to military conscription. Most male U.S. citizens and male immigrant non-citizens between the ages of 18 and 25 are required by law to have registered within 30 days of their 18th birthday. As of the end of 2008, the names and addresses of over 14 million men are on file.