In this document we show the main advances in Quality Service control, provided by the Distribution companies which supply power for the city of Buenos Aires and its surroundings, involving approximately 5 million customers. We have particularly addressed aspects related to the Technical Product (i.e. voltage level and .distortions) and to the Technical Service (i.e. frequency and duration of interruptions). Controls started in September 1993, one year after the first privatizations were made, by means of performance global indicators of companies, to change, since 1996, into idividual indicators for each customer. We could mention that, as a consequence of controls and penalties imposed, the companies have improved the service quality level, thus evidencing their response to the clear economic signals they received. They have had to make investments, not only in those facilities directly affected to the service supply, but also in the management tools which allowed them to acknowledge the situation and take the necessary correction measures.Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE
