Well-developed 3-D spatial skills are critical to success in a number of scienti®c and technical careers. This is particularly true for engineers who generally communicate by graphical means. In the fall of 1992, Baartmans and Sorby received funding from the National Science Foundation (NSF) to develop a course and the course materials for the improvement of 3-D spatial visualization skills for engineering students. In January of 1998, Sorby and Baartmans along with a third PI, Wysocki, received additional funding from the NSF to develop multimedia software and a workbook for the improvement of 3-D spatial visualization skills for engineering students. The multimedia software has been developed in modular form, and there are nine total modules currently available. This article presents the development of the multimedia software and assessment results from its use in special courses designed to improve spatial skills.ß