The department of Social and Organizational Psychology of Leyden University carried out a research project on the effectiveness of behavior modification strategies in influencing energy use in family households. A field experiment was carried out testing the effects on conservation of four strategies. These strategies were: (1) general information about how to conserve energy in the home, (2) weekly feedback with respect to the magnitude and financial consequences of people's personal energy consumption. (3) weekly feedback with respect to the magnitude and financial consequences of people's personal energy consumption compared with the consumption of people in comparable settings (i.e. same houses), (4) weekly comparative feedback and financial reinforcement for decreases in energy use. The results indicate that individual feedback (strategy 2) and financial reinforcement with comparative feedback (strategy 4) are effective in reducing energy use; that comparative feedback (strategy 3) is effective under certain conditions; and that general information (strategy 1) is not effective. The relation between residents' attitudes and their consumption levels is discussed.