For medical professors, it is in their interest to encourage critical thinking (CP) in their students, however, factors such as understanding the meaning of the term, time and the amount of curricular content hinder this objective. Although various efforts have been made, it may be that the teacher is left with the uncertainty of the progress made by his students in this process that leads to medical reasoning, or it may be that he is satisfied with having encouraged this thinking without having an objective estimate that it has occurred. This research presents the didactic strategy of Problem-Based Learning (PBL) and a qualitative technique with which it was possible to carry out the observation record that allowed the identification of CP skills, according to Ennis' taxonomy, in a PBL session. It is possible to make use of the observation record during the PBL sessions, in order to, at first, note the actions of the students when addressing a PBL scenario during its resolution and then perform the categorization and numerical estimation with which it could be seen that the analysis of information is the category that was carried out with the highest frequency (28.7%). which was mostly made up of the ability to ask questions and answer clarifying questions. We consider, on the one hand, that the PBL strategy, in addition to allowing the teacher to comply in a timely manner with the revision of the thematic contents of the subject he teaches, will simultaneously promote the skills of the PC in his students, in addition, the teacher will behave as an observer who will be able to carry out the competence of teacher-researcher and will be able to verify the development of certain skills.