Background Social networking (SN) has become ubiquitous in modern culture. The potential consequences of revealing personal information through SN websites are not fully understood.

Objective To assess familiarity with, usage of, and attitudes towards, SN websites by admissions offices at US medical schools and residency programmes.

Methods A 26-question survey was distributed in autumn 2009 to 130 US medical school admissions officers and 4926 residency programme directors accredited by the Accreditation Council for Graduate Medical Education.

Results A total of 600 surveys were completed, with 46 (8%) respondents who self-identified as reviewing only medical school applications, 511 (85%) who reported reviewing residency programme applications and 43 (7%) who reported reviewing both. 90/600 (15%) medical schools or programmes maintain profiles on SN websites and 381/600 (64%) respondents reported being somewhat or very familiar with searching individual profiles on SN websites. While a minority of medical schools and residency programmes routinely use SN websites in the selection process (53/600; 9%), more than half of respondents felt that unprofessional information on applicants’ SN websites could compromise their admission into medical school or residency (315/600; 53%).

Conclusions SN websites will affect selection of medical students and residents. Formal guidelines for professional behaviour on SN websites might help applicants avoid unforeseen bias in the selection process.