http://en.wikipedia.org/wiki/United_States_MarinesAs of fiscal year 2002 (FY02), it consisted of 480,000 soldiers on active duty and 555,000 in reserve (350,000 in the Army National Guard (ARNG) and 205,000 in the Army Reserve (USAR).
The Marine Corps is the second smallest of the five branches (Navy, Marine Corps, Army, Air Force, Coast Guard) of the U.S. military, with 172,000 active and 40,000 reserve Marines as of 2005.