Objectives High-quality teaching performance is important to ensure patient safety and encourage residents’ learning. This study aims to explore the content and phrasing of suggestions for improvement that residents provide to support excellent teaching performance of their supervisors.

Methods From February 2010 to November 2011, 577 residents were invited to evaluate 501 teachers from both surgical and medical residency training programmes from 20 hospitals. Feedback was collected through a validated formative feedback system named System for Evaluation of Teaching Qualities. Two researchers independently coded the suggestions for improvement with literature-based coding schemes on (1) content and (2) linguistic characteristics. Besides these qualitative outcomes, descriptive statistics were calculated using SPSS.

Results In total, 422 residents (73%) evaluated 488 teachers (97%), yielding 4184 evaluations. Of all teachers, 385 (79%) received suggestions for improvement focusing on teaching skills (TS), 390 (80%) on teaching attitude (TA) and 151 (31%) on personal characteristics. For 13%–47% of the suggestions for improvement, residents added (1) the location or situation where the observed TS or TA had taken place, (2) concrete examples of what teachers could do to improve or (3) (expected) effects of what the change in TS or TA would mean for residents.

Conclusions Residents provide mainly relevant suggestions for improvement that mirror important aspects of teaching performance. However, these comments often lack specific phrasing limiting their value for performance improvement. Therefore, residents are recommended to increase the specificity of the suggestions for improvement. The paper provides directions to phrase narrative feedback.