The American Medical College Application Service (AMCAS) is a service run by the Association of American Medical Colleges through which prospective medical students can apply to various medical schools in the United States. It thus acts as something of a Common Application among the schools.
Most US medical schools granting Doctor of Medicine (M.D.) degrees require that students apply through AMCAS. However, there are seven M.D. schools that do not participate in AMCAS. These schools use the Texas Medical & Dental Schools Application Service (TMDSAS). There are a total of 141 M.D. granting medical schools in the U.S. that use AMCAS, which includes 4 Puerto Rico schools.
Osteopathic medical schools (granting Doctor of Osteopathic Medicine, or D.O., degrees) have a similar system called the American Association of Colleges of Osteopathic Medicine Application Service (AACOMAS).