Tested the effect of 1-sided (favorable argument only) and 2-sided (both favorable and unfavorable arguments) persuasive messages about energy conservation (EC) on attitudes toward EC of 85 preservice elementary teachers, who were categorized as developmentally or nondevelopmentally advanced in knowledge of EC. Ss completed an EC attitude scale before, immediately after, and 4 wks after receiving the persuasive message to assess the effects of the messages on their attitudes. Results indicate that 2-sided communication was more effective than 1-sided communication, regardless of Ss' level of developmental advancement, when attitude change was measured immediately following treatment. Positive attitude change dissipated 4 wks after exposure to the 2-sided communication for developmentally and nondevelopmentally advanced Ss alike. While the attitudes of nondevelopmentally and developmentally advanced Ss exposed to the 1-sided communication did not change immediately after exposure, nondevelopmentally advanced Ss exhibited a positive shift in attitude 4 wks following the presentation of the communication.