OBJECTIVE An important and yet underexplored issue in medical education concerns the extent to which students retain early taught theoretical knowledge during subsequent stages of their academic schooling. This study aimed to assess the degree to which medical students retain basic pathophysiological knowledge on biological psychiatry across different stages of medical education. METHODS A cross-sectional investigation was conducted using a multiple choice questionnaire (MCQ) of objective pathophysiological knowledge taught in a course given to second-year students, supplemented by questions measuring subjective interest and attributed importance to the content taught. Comparisons (ANOVA with post hoc Tukey tests) were carried out among five groups (n = 417): baseline (freshmen), pre-intervention group (second-year students attending the first day of the course), immediate tested group (second-year students on the final day of the course), 1-year delayed tested group (third-year students), and 3-years delayed tested group (interns). RESULTS In comparison to the baseline and pre-intervention groups, the other three groups that received teaching displayed significantly better levels of knowledge (p < 0.0001). Differently, scores of interest and attributed importance were higher in the pre-intervention group relative to all other groups that were tested after having been given the course (p < 0.005). There were no significant associations between knowledge retention, attributed importance, and interest within pre-intervention or post-intervention groups. CONCLUSIONS The only modest loss of knowledge over time indicates that a large proportion of early taught content is retained throughout the later years of medical education. Nevertheless, retained knowledge does not seem to be associated with subjective interest and attributed importance to such early taught content.