This case study describes the design of a video tape presentation for use in a college physiology laboratory. A goal of this color film is to demonstrate to the students those techniques involved in anaesthetising and preparing a frog for a laboratory experiment on the reaction of the heart to electrical and chemical stimuli. The film first shows the preparation procedures in normal order, without commentary, and then those same procedures in reverse order (backward chaining) with commentary. The second part of the film shows additional procedures in normal order with commentary. A student handout accompanies the film. Third year biology students were given a questionnaire to evaluate the film for quality of presentation and didactical design. Overall results indicated that the film was a success didactically. The quality of the instructor's presentation in the film and the use of backward chaining received high positive ratings from the students sampled. (MA)