Almost all U.S. medical schools require applicants to take and submit scores for the Medical College Admission Test (MCAT), a computer-based, standardized examination administered by the Association of American Medical Colleges (AAMC), as part of the admissions process. The MCAT is designed to assess applicants' problem solving, critical thinking, analytical, and writing skills in addition to their knowledge of science concepts and principles prerequisite to the study of medicine.
As one of the few objective measures available to compare applicants and a fairly reliable indicator of applicants' future academic success in medical school, medical school admissions committees place a great deal of weight on MCAT performance. Moreover, the MCAT will probably be one of the longest and most challenging exams you have taken to date. Given the importance of your MCAT score in the admissions process and the difficulty of the exam itself, it goes without saying that devoting a significant time and effort into preparing for the MCAT should be a top priority as you prepare to apply to medical school.
The MCAT is administered multiple times per year at testing centers around the country and advance registration is required. The best source of information about the MCAT can be found on the AAMC web site (see links below.) When to take the MCAT is a personal decision with many factors to consider.