Health plans and Medicare are using cost profiles to identify high-cost physicians in the hope of lowering total health care spending, but it is unclear which types of physicians will be most affected. Using cost profiles created from health plan claims, we examined which physician characteristics are associated with higher costs. Our strongest association was related to a physician’s year of experience. Compared to the most experienced physicians, the least experienced physicians had 13 percent higher overall costs. We found no association between costs and other factors such as malpractice claims, disciplinary action, board certification status, and the size of the group in which the physician practices. While winners and losers are inevitable in any cost profiling effort, physicians with less experience are more likely to be negatively affected by policies that utilize cost profiles. For example, they could be excluded from high-value networks or receive lower payments under Medicare’s planned value-based payment program. Further, our results raise the possibility that the more costly practice style of newly trained physicians may be a driver of rising health care costs.