This article describes the methodology and results of the Rational Use of Energy Program carried out in 29 industries in Medellín, Colombia. Higher energy savings than the ones expected were found in the companies audited. Potential savings are around 24 percent in thermal energy, 11.4 percent in electricity, and 29 percent in electric peak shaving. Recommended actions included adequate operation of processes and equipment, satisfactory maintenance practices, and the implementation of new technologies. An important result is that about 50 percent of all savings could be carried out without investment. A strategic plan has been developed to verify the implementation of the recommendations and the achievement of the improvements. The program was carried out by the Energy and Thermodynamics Group of the Universidad Pontificia Bolivariana, a research center similar in its functions and structure to the Industrial Assessment Centers in the U.S.A. The program was sponsored by Empresas Públicas de Medellín (EPM) Medellín's public utility, and the industries grouped in the Asocilación Nacional de Industriales (ANDI), the national association of industries.