The design of small specialty chemical plants is dealt with in the first part of this paper. The influence of different parameters on decision making between batch and continuous operation was taken into account. The results in the first part of the paper confirm the conclusions from the previous two papers that in the case of single-purpose equipment, the continuous plant is more profitable than the batch one for all capacities, but the batch process with multi-purpose equipment can be favoured over the continuous one when the equipment arrangement is appropriate (minimum number of process units and small size factor). In the second part of the paper, important economic factors (variable, fixed and equipment capital costs, product price) which have an influence on the net present worth of batch and continuous plants are discussed in detail. Variable costs have the greatest effect on the net present worth. Increased variable costs reduce the profitability of the batch or the continuous project. Merging of tasks makes the batch alternative more attractive at small production rates because economy of scale has a stronger effect on small size equipment. Merging can offset other disadvantages of batch processes, therefore it is cheaper to have one larger unit than many small units. The limiting capacity was determined where the batch process becomes more profitable than the continuous one. It depends on the process type and its annual costs. The manufacture of dibutylphtalate from butanol and phthalic anhydride is discussed as an additional case study.