The deferred standard concept can help the operator in controlling on-line the reliability of any process or laboratory gas or liquid chromatographic apparatus. However, more sophisticated auto-control of the chromatograph can be achieved by computerizing the interpretation of some chromatographic quantities for the deferred standard such as peak area, peak height and retention time, and can discriminate among the sample injection, the separation or the detection systems as sources of problems. This approach has been made possible owing to a commercial computing integrator which, in addition to quantitative information, displays messages about the status of the chromatograph. This permanent auto-control suggests what the control unit of a modern process gas or liquid chromatograph, which has to be included in a closed loop control, should be.