Process control systems are being increasingly introduced in pharmaceutical production plant. They exercise quality-relevant functions and are thus subject to legal requirements of validation. It must therefore be established and documented that a process control system fulfills specific requirements. The technical part of this task lies in qualification of the process control system. The present article described the basic principles of such process control system qualification, services for setting up a process control system with obligatory validation, qualification-oriented control system functions, and support of the control system manufacturer in validation.