AMCAS vs. AACOMAS vs. OMSAS: Medical School Application Systems Compared

Three Systems, One Goal

If you are applying to medical school in North America, you will likely encounter at least one of three centralized application systems: AMCAS for US allopathic (MD) schools, AACOMAS for US osteopathic (DO) schools, and OMSAS for Ontario medical schools in Canada. Each system has its own structure, deadlines, and quirks. Understanding the differences before you start can save you weeks of confusion and help you submit stronger applications.

Side-by-Side Comparison

Personal Statement

AMCAS gives you 5,300 characters to explain why you want to become a physician. The prompt is open-ended, and you can approach it from any angle.

AACOMAS also allows 5,300 characters, but the prompt is more specific: why do you want to pursue osteopathic medicine? You must address the DO philosophy directly.

OMSAS does not include a centralized personal statement. Instead, individual Ontario schools require their own supplementary essays through separate portals. This means you may need to write four to six different essays depending on how many schools you apply to.

Key takeaway: If you are applying through both AMCAS and AACOMAS, you need two distinct personal statements. You cannot recycle the same essay.

Activities and Experiences

AMCAS allows up to 15 activities with 700-character descriptions each. You can designate three as "Most Meaningful" and receive an additional 1,325 characters for each.

AACOMAS has no cap on the number of experiences you can list, but there is no "Most Meaningful" designation and no extra character space for highlighted entries.

OMSAS uses the Autobiographical Sketch (ABS), which is fundamentally different. Each entry gets only 150 characters - roughly one sentence. The ABS is organized by category (Employment, Volunteer, Extracurricular, Awards, Research, Other) and requires a verifier for each entry.

Key takeaway: The ABS demands a completely different writing approach. You cannot adapt your AMCAS descriptions for OMSAS - you need to rewrite everything in a compressed, impact-first format.

Letters of Recommendation

AMCAS accepts 3 to 10 letters. Most schools recommend 4 to 5, including science faculty, non-science faculty, a physician, and a community or research mentor.

AACOMAS accepts 2 to 6 letters. At least one should come from a DO.

OMSAS requirements vary by school. Some Ontario schools require specific letter formats or confidential assessments rather than traditional recommendation letters.

GPA and Academic Records

All three systems recalculate your GPA using their own formulas, which may differ from your university's calculation.

AMCAS separates your cumulative GPA from your science GPA (BCPM: Biology, Chemistry, Physics, Math).

AACOMAS also calculates a science GPA, but the included courses and grade replacement policies differ from AMCAS.

OMSAS reports your GPA as calculated by your undergraduate institution, though some Ontario schools apply their own weighting formulas (such as dropping your lowest year or weighting recent years more heavily).

MCAT Requirements

All three systems require the MCAT, but expectations differ:

AMCAS: Median matriculant score is approximately 511-512. Competitive schools often have medians above 515.

AACOMAS: Median matriculant score is approximately 504-506. Top DO programs may have medians closer to 510.

OMSAS: Requirements vary by school. The University of Toronto and Western tend to expect 128+ per section (512+ total). McMaster places less emphasis on MCAT relative to CASPer and GPA.

Additional Requirements

CASPer is required by most Ontario medical schools (OMSAS) and some US schools. It is a situational judgment test that evaluates your personal and professional characteristics.

Casper is not required for most AMCAS or AACOMAS schools, though a growing number of US programs are adopting it.

Secondary applications are sent by individual schools after they receive your primary (AMCAS or AACOMAS) application. These include school-specific essay prompts and additional fees.

Timeline Comparison

The application timelines differ significantly between the US and Canadian systems:

AMCAS and AACOMAS (US):

• May: Applications open and can be submitted
• June-July: Verification period (submit early to avoid delays)
• July-October: Secondary applications
• September-March: Interview season
• October-April: Acceptance decisions

OMSAS (Canada):

• June-July: Application opens
• October 1: Hard submission deadline (no rolling advantage)
• October-December: Supplementary applications and CASPer
• January-April: Interview invitations and interviews
• May: Offers of admission

Key takeaway: US applications reward early submission through rolling admissions. OMSAS has a fixed deadline with no early advantage, but you still need time to complete school-specific supplements after submitting.

Applying to Multiple Systems

Many pre-med students apply through more than one system to maximize their chances. If you are a Canadian student considering US schools, or a US student interested in Ontario programs, here is what to keep in mind:

Applying AMCAS + AACOMAS: You need two personal statements (one general, one DO-specific). Your activities can be similar but should be tailored to each format. Budget for double the application fees.

Applying AMCAS + OMSAS: The ABS requires completely rewriting your activities in 150-character format. OMSAS school-specific essays are separate from your AMCAS personal statement. The timelines overlap but the OMSAS deadline (October) comes after most AMCAS primaries are submitted.

Applying all three: This is a significant time investment. Start your personal statements and activities descriptions in January or February so you are not writing everything from scratch when applications open in May.

Which System Is Right for You?

Apply through AMCAS if you want to attend a US MD program. This covers the vast majority of American medical schools.

Apply through AACOMAS if you are interested in osteopathic medicine or want to broaden your options beyond MD programs.

Apply through OMSAS if you are a Canadian student (particularly from Ontario) or an international student eligible for Ontario medical schools.

Apply through multiple systems if you want to maximize your chances and are willing to invest the additional time and money in tailored applications.

Connecting Your MCAT Prep to Your Application Strategy

Your MCAT score influences which systems and schools are realistic targets. A score of 515+ opens doors at competitive MD programs. A score in the 505-510 range may make DO programs a strong strategic addition. For Canadian schools, section-specific scores matter as much as the total.

Whatever your target, starting MCAT prep early gives you the flexibility to retake if needed and submit your applications on time.

Explore our MCAT prep course rankings to find a program that matches your study style, timeline, and budget.