Admissions to Master of Science programs is limited to holders of the baccalaureate degree, typically the Bachelor of Science, but some schools will consider candidates with a Bachelor of Arts degree, particularly if they have fulfilled a requisite number of science courses.
MS programs typically require one to two years of graduate-level course work. Labs are required for MS programs in experimental sciences, although this requirement is waived in programs like Northwestern University's Master of Science in Education.
Graduate schools typically require master's degree candidates to complete a minimum residency requirement (usually equal to the coursework requirement, one to two years). This requirement is especially significant for students who wish to transfer credit for coursework done elsewhere to the program granting the degree.
At the conclusion of the coursework, many schools require master's degree candidates to sit for comprehensive examinations. These examinations are typically administered by a departmental committee, and have both an oral and written component. Some fields require examination in second languages, as well.
Finally, some master's programs require students to complete a major thesis as a graduation requirement. This thesis varies in length from discipline to discipline, but it is intended as a novel addition to the body of world knowledge in the field. The demands for a master's thesis are not as rigorous as a doctoral thesis, but the task can be daunting, and represents a significant level above research at the undergraduate level.