BackgroundLectures remain an important teaching method to present and structure knowledge to many students concurrently. Adequate measures are necessary to maintain the quality of the lectures. The aim of this study was to determine the impact on the lecture quality using written structured feedback and to compare the ratings of surgical lectures between students and surgical peers.MethodsProspective analysis of two consecutive surgical lecture series for undergraduate students at Goethe-University Medical School was performed before and after evaluation of the lecturers via independent written feedback from trained undergraduate students and surgeons. The 22-item feedback instrument covered three areas of performance: content, visualization, and delivery. Additional suggestions for improvement were provided from both students and surgical peers who anonymously attended the lectures. The lecturers, experienced surgeons, as well as the student and peer raters were blinded in terms of the aim and content of the study. Their response to the feedback was collected using a web-based 13-item questionnaire.The Kendall’s-W coefficient was computed to calculate inter-rater reliability (IRR). Differences between ratings before and after feedback were analyzed using Student’s t-test for dependent samples. The Kolmogorov-Smirnov-test was used for independent samples.ResultsA total of 22 lectures from a possible 32 given by 13 lecturers were included and analyzed by at least three surgeons and two students. There were significant improvements in overall score as well as in the details of 9 of the 13 items were found. The average inter-rater reliability was 0.71. There were no differences in the ratings as a function of the rater’s level of expertise (peers vs. students).We found that 13/23 lecturers (56.5%) answered the questionnaire, and 92% strongly agreed that the written feedback was useful. 76.9% of the lecturers revised their lecture based on the written feedback requiring on average 112.5 min (range from 20 to 300 min).ConclusionsOverall, this study indicates that structured written feedback provided by trained peers and students that is subsequently discussed by the lecturers concerned is a highly effective and efficient method to improve aspects of lecturing. We anticipate that structured written feedback by trained students that is discussed by the lecturers concerned will improve lecturing.Electronic supplementary materialThe online version of this article (doi:10.1186/s12909-016-0806-y) contains supplementary material, which is available to authorized users.