Abstract: The present invention provides a method for producing a concentrated antibody preparation that includes the steps of: (a) obtaining an initial antibody preparation that is an aqueous solution of antibodies and histidine or acetate buffer at a concentration in the range of from about 2 mM to about 48 mM; and (b) subjecting the antibody preparation to membrane filtration so as to remove water and buffer but not antibodies from the antibody preparation, thereby producing an antibody preparation having a higher concentration of antibodies than the initial antibody preparation. The concentrated antibody preparations produced by the method have lower viscosity and are more stable than those of other formulations. The invention further includes concentrated antibody preparations produced by the method, pharmaceutical compositions made using such preparations, and therapeutic methods in which such pharmaceutical compositions are administered to treat diseases.