Each year, the AMA (American Medical Association) releases their "State Medical Licensure Requirements and Statistics." In 2010, we see that sixty-two boards require continuing medical education (CME) for license reregistration. Some states also mandate CME content, such as HIV/AIDS, risk management, or end of life palliative care.
It still baffles me to think that some states still don't require physicians to participate in CME in order for them to renew their medical license. How will we know if these physicians are up-to-date on the latest evidence-based guidelines? When will these states catch up with the others and mandate CME for their physicians? Over 50% of what we learned in medical school is probably wrong. We simply don't know which half, but over time research is revealing what's correct vs. incorrect.
You can view the 2010 state medical licensure requirements on the AMA website (PDF).