What is the difference between AACOMAS and AMCAS?

Dear Applicant,

Two different organizations run AMCAS and AACOMAS. The AAMC describes AMCAS as "the AAMC's centralized medical school application processing service." AACOM describes AACOMAS as "the centralized online application service for U.S. colleges of osteopathic medicine." Same job, different owners, and a handful of rules that quietly diverge.

AMCAS is operated by the AAMC, the Association of American Medical Colleges. The AAMC says "Most U.S. medical schools use the AMCAS program as the primary application method for their entering classes," and that "The AMCAS program is only available to the first-year entering classes at participating U.S. medical schools."

AACOMAS belongs to the American Association of Colleges of Osteopathic Medicine, which says of its service: "We verify your application for accuracy, process it and send it with your materials to those osteopathic medical schools you designate." Its applicant help center states that "All accredited US osteopathic medicine programs" participate, with two exceptions, UNTHSC-TCOM and Sam Houston State University College of Osteopathic Medicine, whose applicants "must use the separate Texas Medical and Dental School Application Service."

Texas is one place where the two systems rhyme. The AAMC: "To apply to an MD program at a public medical school in Texas, you will need to apply using the Texas Medical and Dental Schools Application Service (TMDSAS)."

AACOMAS publishes a dated table. Its first row reads: "The AACOMAS application cycle opens. May 4, 2026." The cycle closes "August 2, 2027 at 11:59 PM ET," and "All application processing ends. August 5, 2027 at 5 PM ET."

AMCAS opened one day later. The 2027 AMCAS Application Workbook says: "Beginning May 5, 2026, you may initiate your 2027 AMCAS application at www.aamc.org/amcas."

AMCAS leaves deadlines to the schools. The AAMC: "All application deadlines are set by individual medical schools," and "Your application must be submitted to the AMCAS program (not processed) by 11:59 p.m. ET to meet the deadline." AACOMAS publishes its own cycle dates and notes that a program's date can differ from them: "In some instances, the individual program's deadline may differ from the application's cycle dates." Either way, "You can submit your application up until 11:59 PM ET on the deadline date."

AMCAS: "The 2027 application fee is $180 for the first school and $48 for each additional school."

AACOMAS: "AACOMAS charges $198 for the first program you apply to and $60 for each additional program."

Fee help is one place the two differ. The AAMC's Fee Assistance Program provides a "Waiver for all AMCAS application fees for one (1) submission, covering up to 20 medical school submissions ($1,092 value), submitted by Dec. 31, 2027." AACOMAS waivers are narrower, and limited in number: "Each fee waiver covers only the initial application fee, so if you wish to apply to additional programs, you are responsible for the remaining balance." They go out in "a limited number" and "on a first-come, first-served basis," and "You must request a fee waiver before you submit your application. Requests received after an application has been submitted will not be honored."

On repeated courses the two services say the same thing. AMCAS: "The AMCAS program counts grades for all attempts of a repeated course, even if your school does not." AACOMAS: "AACOMAS does not recognize an individual school's policies for forgiveness, academic renewal, or grade replacement for repeated courses," and "All grades earned for repeated courses are factored into your AACOMAS School GPA."

AMCAS adds a step for forgiveness policies. If a school replaced an original grade with a special transcript symbol, "the original grade and attempted credits must be entered on your AMCAS application, regardless of whether they appear on your official transcript." Leave it out and "the AMCAS program will return your application to you to enter the original grade, which may cause you to miss application deadlines and forfeit fees."

A difference that is easy to miss is where the math lives. AMCAS: "The BCPM GPA is comprised of Biology, Chemistry, Physics, and Mathematics courses. All other coursework will be calculated in the AO (All Other) GPA." AACOMAS divides each year into "Science, Non-Science, and Total (science plus non-science) sections." Its science list is "Biochemistry, Biology/Zoology, Inorganic Chemistry, Organic Chemistry, Other Sciences, Physics." Its non-science list is "Behavioral Sciences, English, Mathematics, Other Non-Science." The same calculus grade sits inside the science GPA on one application and outside it on the other.

Credit hours convert differently too. AACOMAS states a fixed ratio: "AACOMAS calculates all GPAs in semester hours. Courses that were completed in quarter hours are converted to semester hours. The conversion ratio is 1.0 quarter hour = 0.667 semester hours." AMCAS says your application "will automatically convert most undergraduate credit hours (also known as units and hours) to either semester hours or supplemental hours based on conversions provided by undergraduate institutions."

Both cap at ten. AMCAS: "You may have up to 10 letters associated with your AMCAS application." AACOMAS: "You can enter information for a maximum of 10 evaluations," and "If you want to submit more, send those additional evaluations directly to your programs." On AACOMAS, "a committee letter only counts as one evaluation and the individuals who contributed to the letter may not be used as additional evaluators."

Neither requires letters before you submit. AMCAS: "Letters are not required to submit your application, or have your application verified by the AMCAS program." AACOMAS: "You can submit your application before your transcripts and evaluations are received."

After submission they part ways. AMCAS: "you can only make additions of up to 10 letters, and you must notify the AMCAS program if you have a letter you wish to no longer be sent to medical schools; you cannot delete letters of evaluation from your application." AACOMAS: "You can edit and delete evaluations with Requested or Accepted statuses."

None of the pages fetched for this article say whether one person may use both. What both do say is that programs can be added after submission. AACOMAS: "You can select additional programs to apply to." AMCAS: "You can send your application to additional medical schools if their application deadlines have not passed." AMCAS adds that the list cannot shrink: "Once you have submitted your application to the AMCAS program, you can't remove or substitute schools on your designation list under any circumstances."

So these are two separate systems with separate fees, separate waivers, and separate school lists. Whether both belong in one person's plan is a question for your prehealth advisor, not for a newsletter.

Alex