This paper considers the plantwide control of continuous processes that produce multiple products. A typical example is a process in which there are two reversible reactions producing two products M and D: A + B double left right arrow M + C and A + M double left right arrow D + C. The control structure must be able to achieve different production rates of the two products. Several conventional control structures are studied in which the flow rates of the fresh feed streams are fixed or manipulated by level or composition controllers and the production rates of the two products are not directly set. Several "on-demand" control structures are also developed in which both product streams are flow-controlled. The control system must adjust the conditions in the plant and the fresh feed streams to achieve the desired product flow rates. The most effective on-demand control structure requires no reactor composition analyzer and no recycle of product streams.