Experimental studies done previously in our group showed a great potential of hollow fiber modules as extraction apparatus, especially in environmental engineering, where the main advantage of the technique, i.e., the possibility to concentrate metallic species in a cycle of extraction and stripping processes, is exploited. The new developments of Hoechst-Celanese are 'liqui-Cel(R) Extra-Flow' hollow fiber modules, which are characterized by cross flow of fluids. Additionally, the applied technique of fabrics wound enables an easy scale-up of the membrane contactor by enlarging its diameter. In order to calculate concentration profiles for this new way of phase conduction it is urgent to know the values of the mass transfer coefficient in the shell side of the module. In this paper the correlation for calculating the mass transfer coefficient of various cross flow modules has been established being as Sh = 1.76.(ReSc0.33)-Sc-0.82.. It is shown that this procedure unites the different geometries of various cross flow hollow fiber modules.