Constructive feedback is defined as the act of giving information to a student or resident through the description of their performance in an observed clinical situation. The following keys are required during feedback in order to get student's performance improvement: the observation of an event, the instructor's comment on said performance, by following always a pre-established pattern or standard, and advice on improvement. Major impact takes place when a student or a resident compares the teacher's feedback to its own performance. The dissonance between desired and actual performance constitutes a strong motivation and deep-learning generator. Most of the teachers find it essential, but in general they carry it out in a short and non specific way. Medical students and residents are willing to get and need constructive feedback and they clearly associate it to high-quality learning. However, even though they appreciate it, they seldom request it. It is essential to take maximum advantage of feedback by giving recommendations, producing reactions and self-analysis and also by defining an appropriate action plan. It takes time and effort to apply this tool, but it is of great value for the growth and academic development of students and residents.