Plantwide control involves the systems and strategies required to control an entire chemical plant consisting of many interconnected unit operations. A general heuristic design procedure is presented that generates an effective plantwide control structure for an entire complex process flowsheet and not simply individual units. The nine steps of the proposed procedure center around the fundamental principles of plantwide control : energy management; production rate; product quality; operational, environmental and safety constraints; liquid-level and gas-pressure inventories; makeup of reactants; component balances; and economic or process optimization. Application of the procedure is illustrated with three industrial examples : the vinyl acetate monomer process, the Eastman plantwide-control process, and the HDA process.