What can make the answer to this question more transparent than looking up at the application eligibility criteria that some residency programs have put up on their websites ? :-)
Let's look at some quick samples :1. Eastern Virginia Medical School
Family practice Residency program:
"To be competitive, an applicant should have a CV that shows real interest in family practice or primary care medicine. U.S. experience should include family practice experience, or at least a combination of U.S. experiences that together define family practice (such as several months each of internal medicine, pediatrics, and OB/GYN)."
The Internal Medicine Residency Program at the same place says:
"Must have completed at least 12 months hands-on clinical experience within the United States"
2. Georgetown University hospital
Psychiatry Residency Program:
"We are generally looking for applicants who have
graduated from medical school within the past ten years, and who have approximately two years of U.S. clinical experience (either a third and fourth year of American Medical School or approximately two years of U.S. clinical experience for International Medical Grad

uates)."
3. Griffin Hospital
Internal Medicine Residency Program:
"1 year US clinical experience is preferred but not mandatory"
- in such cases, given the flood of IMGs, it's safe to assume that though Clinical Experience is not technically needed, functionally it is !
4. University of Kentucky
Anesthesiology Residency Program"For International Medical Graduates, we also require a current ECFMG certificate and recommend at least 3 months of clinical experience that included patient care (not Observership) in the US, Canada, or UK; or at least 2 years anesthesia experience in other foreign countries.
5. Some Programs may even want you to be already worked as a resident in the USA to be eligible. For example, here's what the Fort Collins
Family Medicine Residency Program says:
"Unless you have done two years or more of post-graduate medical training in the United States, you are not qualified for consideration for a residency position at the Fort Collins Family Medicine Residency Program"
Enough evidence ? : Some guys often like to call US-Clinical Experience as USMLE Step 4 ;-) . This should hardly be surprising - residency is like a true job with pay and benefits and like any other job (engineering, management, film-making) prior experience is attractive to the prospective employers (program directors).
Note: US Clinical Experience has gained lotsa importance recently in Family medicine ! Most Family Practice Residency Programs have become more stringent in evaluating a candidates sincerity and fidelity to Family practice, since many International Medical Graduates (AMGs too) unfortunately drop the specialty in one-two years and attempt to switch to Internal medicine, psychiatry, pediatrics, etc. Clinical Experience in primary care is evidence of your commitment and sincerity and hence highly valued by program directors to cut-down on specialty shifts by IMGs.
Some pertinent points for IMGs:a. As discussed elsewhere too, Clinical hands-on experience counts more than observerships (as evident on example 4 above, though having an observership is better that nothing at all since it gives you a US - LOR
b. Have a look again at the 4th example above - Experiences outside the US do not go waste, if they are a in a western country setup like Canada and the UK - so if you are around, its good to have something going on clinically in these places too rather than nothing - the idea is to have minimum 'time-gaps' on your resume.
c. The more competitive a Residency is - the more important experience in that clinical or non-clinical specialty becomes
d. If you have to make a choice between clinical experience opportunity at one place and clinical research at the other, it may make more sense to choose the clinical experience option, because during your clinical rotations, you can always find opportunities to hook up with some faculty in the university / hospital to help him/her on research and get research too on your resume.
e. Remember that places that say "We do not require US Clinical Experience" also see thousands of applications with good-score + USCE combination and will naturally prefer such applications - hence do not go light on the need for clinical experience, try your best to get it. Even getting some in UK and Canada might be better than having nothing at all, unless you are already pursuing a post-graduate specialty training in your home country.
f. Observing a private practitioner is on my least advisable list, yet to make the most of it -
Read thisg. A Current residency itself is great US-clinical experience ! That's why they Residents switching specialties are attractive candidates to other residency programs. Since the Last
Q. How long should the Clinical Experience (Observerships, Externships, Electives) be ?A. The longer the better - Up to to 3 Months to 6 Months is great and even more the better. Of course, a few programs do require a year - but then, just like we can't keep all people around us happy at the same time, you cannot satisfy the criteria for every single residency program on the American soil ;-). All we can do is maximize within our means.
Labels: Externships, Observerships, USCE