ESDU 97006 is one of a group of Data Items relating to the selection and costing of heat exchangers. Its objective is to provide the process engineer with a simple and rapid method of obtaining rough cost estimates of industrial-scale plate-fin heat exchangers (PFHE's); such estimates are often required well before the actual configuration of the equipment is decided. ESDU 9006 extends the information in ESDU 92013 so providing updated budget cost estimates for PFHE's obtained from the plate-fin exchanger manufacturer, IMI Marston Ltd. ESDU 97006 discussed the construction, configurations and applications (especially in multi-stream use) of PFHE's. The costing data for PFHE's of brazed aluminium construction are presented in two ways. Firstly, the two-stream costing method of ESDU 92013 is used to provide updated costs related to 'standard' designs for a range of hot and cold streams, including boiling, condensing and cryogenic flows and based on typical fluid pressures. Secondly, a methodology is developed for multi-stream PFHE's in which heat transfer and then costs are estimated on a volumetric basis. This method, which is based on the techniques of process integration, uses stream volumetric film coefficients; values of these coefficients were derived and are presented for the typical working fluids. From the resulting overall volumetric heat transfer coefficients the total volume curve for 2, 3 and 4-6 stream units. Cost factors are also provided which account for increased pressure and stainless steel construction. Details of the calculation procedures used are provided and three worked examples illustrate the use of the method, including a worked example that illustrates the cost saving for a multi-stream unit relative to a multiplicity of 2-stream units. The bases of the approximate design method is given in an Appendix.