The results of a number of studies which have indicated the limited effectiveness of health education efforts using the mass media are reviewed. The cause of these failures, according to the authors was the inability to apply a number of principles of effective design to the instructional materials used in the mass media. The basic slide show produced by the neighborhood health center for its own population may be more effective than a nationally televised spot announcement because locally prepared material can be sharply focused on the learner's characteristics and the specifically desired outcome behavior. The authors list 10 guidelines for the construction of effective instructional materials: define outcome measures, analyze relevant characteristics of the learner, gain and maintain the learner's attention, establish the learner's vulnerability, demonstrate the needs for action, establish the learner as an agent, establish the learner's effectiveness, provide for practice, repeat key facts, and generalize to similar situations. The principles of social reinforcement that must accompany health education instruction if behavior is to be modified are outlined. How environmental factors such as time, distance, expense, and the organization of health services hamper desired behavior outcomes is also discussed.