In the development of improved control systems for the chemical and petroleum processing industries, a need is encountered repeatedly for practical methods of repositioning several final control elements (not necessarily independently) from each of several key primary measurement and control instruments. That is, a need exists to allow controlling a combination of final elements from a combination of primary controllers. For lack of established terminology to describe this general type of a control system, the authors have chosen the name "combination control." The basic idea of combination control is not new. Limited versions of combination systems are well known in the form of cascade controls, blending systems, and computing relays of many types. Also, computer controls result in a type of combination control of complexity commensurate with the sophistication of the computer system. Even so, a gap has existed between the limited capabilities of existing cascade and relay systems, and the more complex and costly computing systems. This paper describes a system for filling this gap which is simple to use and yet overcomes many of the limitations of existing low cost systems. The control system and concepts to be described allow a practical means of combining any reasonable number of control systems to provide repositioning of each final control element from any desired combination of primary measurement control signals. This combination control system results in a significant improvement in the response of fractionation columns to both external disturbances and to changes in operating set points.