Electric Power Industry of Serbia (EPS) performs a variety of system services for the Serbia's Transmission System Operator (EMS). As part of these services, primary frequency control takes very important place. Control of electricity generation and monitoring of electricity flows in the interconnection is problem whose importance is increasing due to deregulation and changes in the concept of management of modern power systems. The aim of this paper is to study the characteristics of the primary frequency control of power system in Serbia as the basis for its improvement.