Two studies evaluated the effects of a group contingency on electricity conservation. In Study 1, residents of 166 apartment units in three towers held meetings and received biweekly payments of the value of electricity saved compared to predicted use. The group contingencies were initiated in each tower in a multiple-baseline design. The program produced substantial savings in one tower (11.2 % of temperature-adjusted baseline), moderate savings in another (4.0%), and minimal savings in a third (1.7%). Overall, the residents saved 6.29%. In Study 2, residents of 255 apartment units, also in three towers, received the same treatment, except only 50% of the value of their savings were paid, and they received a one-time bonus of $5 for using > 10% less than baseline. Towers in Study 2 showed savings of 9.5%, 4.7%, and 8.3%, an average of 6.9%.Over the past several years, there has been a burgeoning interest among social scientists in applying behavioral principles to reduce residential energy consumption. Several studies have demonstrated that regular feedback on energy use can reduce consumption (Becker, 1978;Hayes & Cone, 1977;Kohlenberg, Phillips, & Proctor, 1976;Palmer, Lloyd, & Lloyd, 1978;Seligman & Darley, 1977;Winett, Kaiser, & Haberkorn, 1977;Winett, Neale, & Grier, 1979). Monetary rebates based on decreases in energy consumption have also been shown to be effective means of reducing residential energy use (Winett, Kagel, Battalio, & Winkler, 1978;Winett & Nietzel, 1975 There is a category of residential units in which there is someone with a strong interest in getting residents to conserve energy. These are master-metered apartments, in which residents do not pay for their own energy use directly. Energy conservation benefits apartment owners by reducing their operation costs, and cost-effective incentive or feedback programs may be practical. Master-metered apartments use about 35o% more electricity than similar individually metered buildings (Midwest Research Institute, 1975). Approximately one-third of all apartment units in the U.S. are master-metered and their total waste of electricity is estimated at 9.1 billion kilowatt hours per year.This study evaluated the use of a group contingency for electricity conservation.