A new method allowing the optimal design of baffled shell-and-tube heat exchangers will be discussed in this paper. Tile known commercial design tools do not consist optimization strategies. There are presented as simplified expressions describing interaction between heat transfer and pressure drop that can be used for optimal design of heat exchangers from economic viewpoint. The developed program system HEATDESIGN is realizing a general computer-supported design on the basis of estimation of optimal pressure drops determined by consideration of economic conditions and process data. Examples show the influence of changed economic parameters or process data on the design and costs by means of optimization. In addition the program gives the possibility to optimize components of apparatus.