This study describes and compares the intensity of stress responses, both psychologically and physiologically, to a real and a simulated stressor. The real stressor involved lecturing to a class of students in a post-secondary institution during a practice teaching course. The simulated stressor was a simulated, standardized lecture given in a lecture room to 6 fellow students and 2 members of the university staff. To gain insight into the intensity of the stress responses, the measurements took place before, during, and after lecturing. The adaptation to the stressor after a teaching practice period in which the student teacher gave at least 20 lectures was also studied. Subjective anxiety scores were obtained in both situations from 26 subjects. For 12 of these subjects, heart rate responses were also obtained. The psychological and physiological data indicated that lecturing imposes a severe load on the student teacher, especially at the beginning of the teaching experience. At the end of the practice course, all stress indices showed lower values. Heart rate and subjective anxiety scores indicated that the standardized lecture is experienced as more ego threatening than the real lecture. © 1987 Taylor & Francis Group, LLC.