Method and means for automatically controlling chlor-alkali cells are described. Control is exercised on the basis of a mass flow analysis, starting from a target caustic concentration for the catholyte output, to establish individual set points for optimum cell system operating conditions so as to achieve said target output value. Such control is accomplished by a central automatic control unit which is adapted to monitor the operation of the cell and its associated brine and caustic output subsystems and to institute appropriate corrective actions whenever a tolerance band around one or more of said set points is exceeded.The control unit is further adapted to provide daily and weekly operating summaries and to store said summaries for trends analyses to establish the scope and significance of any long-term degradative processes which might be occurring.