Although assessing professionalism poses many challenges, gauging and detecting changes in professionalism is impossible without measurement. This paper is a review of techniques used to assess professionalism during the past 20 years. The authors searched five electronic databases and reference lists from 1982 to 2002. Eighty-eight assessments were retained and organized into content area addressed (i.e. ethics, personal characteristics, comprehensive professionalism, diversity) and type of outcome examined (i.e. affective, cognitive, behavioral, environmental). Instead of creating new professionalism assessments, existing assessments should be improved. Also, more studies on the predictive validity of assessments and their use as part of formative evaluation systems are recommended. Based on the review, suggestions are presented for assessing medical students, resident physicians and practicing physicians.