While I agree with the last post about looking at the makeup of the residents and faculty, it's still not 100%, and you have to realize that it can become a self-fulfilling prophecy as well. My program is all male resident-wise currently and we haven't had a female resident in the last 5 years, and the last one switched to Radiology after her intern year. We get labeled as a "good ole boys" program and there is no denying that all of our residents are male. That being said, we have rotators every year that are female who are very strong candidates. I have talked to our chiefs on the committee and it seems like every year we have females ranked ahead of people that match at out program. However, since the feeling is out there that we don't have females, females are potentially less likely to rank us highly for fear that there will be a negative atmosphere. So, even though the makeup of the resident pool is not as diverse as maybe you'd like to see, it doesn't mean that there is an aversion to female residents.
So in relation to your original question, I agree that you should look on the program websites at the makeup of the residents to get a general idea. However, definitely don't pidgeon-hole yourself into only programs that appear females friendly. You may find that a program with all males is looking to become more diverse, or perhaps doesn't get many female applicants. As I would advise all medical students, be smart about where you apply and interview, but go for the programs you want and don't let anyone tell you that you can't go here or there if you want.
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