OPC (OLE FOR PROCESS CONTROL) IS AN INDUSTRY STANDARD CREATED IN COLLABORATION OF A NUMBER OF WORLDWIDE LEADING AUTOMATION HARDWARE AND SOFTWARE MANUFACTURERS IN COOPERATION WITH MICROSOFT. THE STANDARD CREATES A COMMON INTERFACE FOR COMMUNICATION BETWEEN VARIOUS DEVICES CONTROLLING TECHNOLOGICAL PROCESSES. THE OBJECTIVE IS TO PREVENT THE GIVEN MONITORING OR CONTROL SOFTWARE FROM BEING DEPENDENT ON THE HARDWARE MANUFACTURER. OPC IS BASED ON THE OLE/COM/DCOM TECHNOLOGY OF MICROSOFT, INC.IT PROVIDES MECHANISMS TO COLLECT THE DATA FROM DATA SOURCES AND COMMUNICATE THE DATA TO ANY CLIENT APPLICATION INDEPENDENTLY ON THE HARDWARE MANUFACTURER. OPC HAS THREE MAIN COMPONENTS : OPC DATA ACCESS, OPC ALARM & EVENT AND OPC HISTORICAL DATA ACCESS AND EACH ONE HAS BOTH CLIENT AND SERVER COMPONENTS ACCORDING TO CLIENT/SERVER ARCHITECTURE. OPC IS WIDELY USED IN DEVELOPING SCADA SYSTEMS. THIS ARTICLE TRIES TO INTRODUCE THE OPC STANDARD AND ITS USAGE IN SCADA INDUSTRY.