Analytical solutions of the effectiveness of membrane mass exchangers, including the effects of dialysis and ultrafiltration, have been obtained for various flow arrangements. The effectiveness of a membrane mass exchanger increases with the increase in the solute mass transfer coefficient, ultrafiltration flux and dialysate flow rate, as well as with the decrease in the retentate flow rate. Based on the same number of transfer units, the mass transfer rate in the counter-current flow arrangement is the largest, and the enhancement of mass transfer by means of the ultrafiltration flux in the co-current flow system is the highest.