A study measured both short- and long-term effects of an educational workshop designed for teachers in the Faculty of Health Sciences, Ben-Gurion, Israel. Participants were 60 volunteer faculty members who were randomly assigned to one of eight multidisciplinary groups for the 4-day workshop, which aimed at improving teachers' instructional behavior in two dimensions: (1) to replace the traditional teaching modality of lecturing by a pattern which elicits students' self-initiated verbalization (activity dimension); and (2) to use and stimulate the students to use a higher cognitive level of verbal exchange during the lesson (cognitive dimension). The workshop was based on microteaching techniques, and each teacher had 3 presentations in 3 successive days and was invlolved in reviewing approximately 18 additional presentations by colleagues. Group discussion followed each presentation as did observation of the videotaped performance by the presentor. After the workshop, 161 lessons of the 60 teachers were observed along 500 days. Results indicated an increase in both the activity and the cognitive parameter. The new level of performance was sustained for the activity parameter along the entire follow up period. And, although the cognitive level moderately declined after 200 days, the instructional behavior was still significantly different after 500 days. (JM)