The United States Marine Corps, or USMC, is one of the branches of the U.S. armed forces. Different branches of the military have different enlistment requirements, but it is possible to enlist in the Marines without a high school diploma. Ninety percent of enlisted Marines are required to hold diplomas, however the Marines have a policy of accepting no more than 5 percent of recruits without one. Enlistees are placed in a three-tier system. Tier 1 recruits hold a diploma, tier 2 recruits have earned a GED and tier 3 recruits have neither.

Meet the age and physical requirements of enlistment. You must be between age 17 and 35 to enlist in the Marines. If you are 17, you will need your parents permission. Physical requirements vary depending on your gender, but generally you must be between 5 feet and 6 feet, 8 inches tall, weigh less than 255 lbs., be able to pass a physical examination and have acceptable vision, either with or without glasses.

Prove your citizenship. You must show that you are a U.S. citizen or a legal immigrant authorized to be a U.S. resident through the term of your enlistment.

Pass the Armed Services Vocational Aptitude Battery, or ASVAB, test. This is a timed test in four parts: Arithmetic Reasoning, Math Knowledge, Word Knowledge and Paragraph Comprehension. You need a minimum score of 31 on the ASVAB to enlist in the Marines. The less education you have, the more important your score becomes.

Enroll in college courses. Having a high school diploma greatly increases your chances of being accepted into the Marines, but you can boost the odds of acceptance if you hold a GED or have no certification by taking a few college-level classes at a local community college. It's a good idea to take courses that will help you with the ASVAB test, such as math or English.

Talk to a recruiter to learn about all of your options. A recruiter can tell you about the various jobs that are available and how best to prepare for enlistment. He also might be able to direct you to resources for completing your GED if you do not have one or for studying for the ASVAB.