Tested was the effect of a one-sided and two-sided persuasive message on the attitudes toward energy conservation of 85 preservice elementary teachers categorized as developmentally or nondevelopmentally advanced with respect to the topic of the message. The study addressed the following questions: (1) Are one-sided and two-sided systematically designed communications more effective in persuading nondevelopmentally advanced and developmentally advanced persons, respectively? (2) Do positive attitude gains between pre- and posttests, if any, dissipate within four weeks following the treatment? The important finding was that the two-sided communication was more effective than the one-sided communication regardless of subjects' level of developmental advancement when attitude change is measured immediately following the treatment. Secondly, positive attitude change dissipated four weeks after exposure to the two-sided communication for developmentally and nondevelopmentally advanced subjects, alike. Thirdly, while the attitudes of nondevelopmentally and developmentally advanced subjects exposed to the one-sided communication did not change immediately after exposure, the nondevelopmentally advanced subjects exhibited a positive shift in attitude four weeks following the presentation of the communication.