State medical boards discipline several thousand physicians each year. Although certain subgroups, such as those disciplined for malpractice, substance use, or sexual abuse, have been studied, little is known about disciplined physicians as a group… A total of 375 physicians licensed by the Medical Board of California (approximately 0.24% per year) were disciplined for 465 offenses. The most frequent causes for discipline were negligence or incompetence (34%), abuse of alcohol or other drugs (14%), inappropriate prescribing practices (11%), inappropriate contact with patients (10%), and fraud (9%). Discipline imposed was revocation of medical license (21%), actual suspension of license (13%), stayed suspension of license (45%), and reprimand (21%). Type of offense was significantly associated with severity of discipline (P=.03). In logistic regression models comparing disciplined physicians with controls matched by locale, board discipline was significantly associated with physicians’ sex (odds ratio [OR] for women, 0.44; 95% confidence interval [CI], 0.28-0.70) and involvement in direct patient care (OR, 2.56; 95% CI, 1.75-3.75). In the regression model with additional matching criteria, disciplinary action was negatively associated with specialty board certification (OR, 0.42; 95% CI, 0.29-0.60) and positively associated with being in practice more than 20 years (OR, 2.02; 95% CI, 1.39-2.92). A small but substantial proportion of physicians is disciplined each year for a variety of offenses. Further study of disciplined physicians is necessary to identify physicians at high risk for offenses leading to disciplinary action and to develop effective interventions to prevent these offenses.