The practice of dissection teaches students not only the foundations of anatomical knowledge but also encourages the development of professional competencies. Yet, the dissection of cadavers in the gross anatomy course can be a stress factor for medical students. There are a minor proportion of students who demonstrate strong emotional reactions in anticipation of being confronted with a cadaver. Therefore, in 2008, the authors implemented a voluntary course entitled, "Anatomical demonstrations of organ systems" (AD-OS) in advance of the dissection course to ease this psychological burden. The question of whether attendees of AD-OS showed less mental distress at the start of the dissection course compared with those that had not or only infrequently visited AD-OS was addressed. AD-OS attendees assessed their expected mental distress using a five-point Likert scale before starting the dissection course and a second time at the end of their first day, after they had been confronted with a cadaver. AD-OS was evaluated as excellent and the majority of students participated actively during teaching sessions. Overall, female students showed higher levels of mental distress. AD-OS attendees assessed themselves as being less burdened by mental distress than members of the control group. Longitudinal analysis revealed that students who visited AD-OS showed a marked decrease of their mental distress level, comparing prospective and retrospective ratings. This was significantly (P less than 0.001; Z = -6.061) different from nonattendees or those who visited AD-OS only infrequently. AD-OS satisfied its intended teaching goals and proved that a step-by-step introduction of dissection through anatomical demonstrations helped to reduce the mental distress of students. Future studies are planned to measure mental distress with objective instruments. (Contains 5 figures and 4 tables.)