Interactive video can be defined as any video system in which the sequence and selection of messages is determined by the user's response to the material. The simplest interactive video programs have the four following elements: the presentation of information (demonstration), the student's opportunity to respond (exercise), the selection by the system of an appropriate response to the input (control), and the presentation of the system's response (feedback). The essence of interactive video instruction is to have a program with as much video presentation of real images as possible. The discs, about the size of a long-play record, store audio and video information in the form of microscopic pits that are created and read by a laser. The capacity to repeat frames, branch through the program, and receive self-paced instruction makes computer-controlled videodisc instruction ideally suited to education and training. This type of training can also be used to create scenarios too dangerous to practice in real-life situations. 5 footnotes.