Members of the public expect practicing physicians to be competent. They expect poorly performing physicians to be identified and either helped or removed from practice. "Maintenance of professional standards" by continuing education does not identify the poorly performing physician; assessment of clinical performance is necessary for that. Assessment may be responsive-ie, following a complaint- or periodic, either for all physicians or for an identified high-risk group. A thorough review using a range of tools is appropriate for a responsive assessment but is not practical for periodic assessment for all. A single, valid, reliable, and practical screening tool has yet to be devised to identify physicians whose practice is suboptimal. Further, articulate commentators are concerned about the harm that too-intensive scrutiny of professional performance may cause. We conclude that high performance by all physicians throughout their careers cannot be fully ensured, but it is nonetheless the responsibility of licensing bodies to use reasonable methods to determine whether performance remains acceptable. Such methods should be shown scientifically to be accurate, valid, and reliable for practicing physicians. Such an approach is likely to encourage the agreement and cooperation of the profession. To do less risks losing the trust of the public.