Context  Measures of professionalism in undergraduate medical students are generally subjective in nature, and based on limited observations of behaviours in observed settings. We have previously described an objective scalar measure of conscientiousness over many occasions, and shown that it correlates with independent faculty estimates of students’ professionalism. In this study we test the hypothesis that these measures of conscientiousness relate to independent peer estimates of professionalism, and explore the relationships between conscientiousness, and gender and educational background.

Methods  Medical students in Years 1 and 2 of an undergraduate programme were invited to estimate the professionalism of fellow students using a peer nomination approach. The correlation with the Conscientiousness Index (CI) for each student receiving nominations was explored statistically. Male and female students, from three educational backgrounds, were also compared on the basis of their CI scores. Developmental properties were considered by comparing Year 2 students’ CI scores with their corresponding Year 1 performance.

Results  There was a statistically significant negative correlation between CI scores and nominations for lack of professionalism. No differences were observed between male and female students. There were occasional differences between students of different educational backgrounds, but the sample sizes of some groups were small and we would not wish to over‐interpret these data.

Conclusions  These results support the use of the CI as a scalar, objective potential measure of professionalism, although the observations require repetition elsewhere and over an extended period of time in order to determine the predictive value of this approach.