UK doctors-in-training undergo assessments of their professional behaviours. From an analysis of multi-source feedback (MSF) data, we report how ratings of junior doctors (Foundation Programme [FP] doctors and senior house officers [SHOs]) differed by staff group. The MSF data were collected in 2003 and 2005 in hospitals in the West Midlands. Using a single-sided Team Assessment of Behaviour form, 1928 assessors evaluated 226 FP doctors and SHOs in four domains: professional relationship with patients; communication; team-working, and accessibility. The distribution of 'concerns' across the professional groups was explored using a random effects logistic regression model. On average, each trainee received nine assessment forms from a range of staff, most commonly nurses. Although concerns were identified for the minority, ratings varied by staff group. Peers (other FP doctors or SHOs) and administrators or managers were four and three times, respectively, less likely to indicate concern. By contrast, consultants and sisters (senior nurses) were more likely to give concern ratings. Guidance on the selection of assessors in any MSF process should take into account findings that rating behaviour varies by staff group.