The relationship between the design of a fines dissolver and the optimal operating conditions of a crystallizer is examined. In the operation of industrial crystallizers, it is typically desirable to produce large crystals since they are easily separated from the liquid phase. Accordingly, this study examines the operating conditions that maximize the production rate of crystals that are larger than a given size. Emphasis is placed on the influence of fines dissolution on the optimal operating conditions. It is demonstrated that when a crystallizer is equipped with a fines dissolver with large internal volume, the production rate of large crystals at the optimal operating condition increases and becomes less sensitive to variations in the operating conditions.