A process for purifying immunoglobulin G (IgG), from a crude plasma protein fraction, which comprises preparing IgG supernatant by precipitating of a high portion of non-IgG proteins, filtering the supernatant by means of an anion exchange resin and a cation exchange resin connected in series, washing out protein contaminants and eluting IgG, performing a dia/ultrafiltration on the IgG-containing eluate, inactivating viruses in the eluate, performing further filtration of the eluate by means of an anion exchange resin and subsequently a cation exchange resin, eluting contaminants and subsequently eluting IgG and performing dia/ultrafiltration on the resulting eluate for concentrating IgG until the conductivity is less then or equal to 1 mS/cm, wherein all steps are performed by using suitable buffers and without denaturating any of the components. In addition, disclosed is a liquid IgG product having a purity of more than 98 %, a content of IgG monomers and dimmers of more than 98.5 %, a content of IgA of less than 6 mg IgA/l, and containing IgG1, IgG2, IgG3 a IgG4, wherein the IgG concentration is 1 to 20 % by weight. Also, proposed is a use of that product for the preparation of a medicament for the treatment of mammals including humans suffering from primary or secondary immune deficiency as well as from other diseases.A process for purifying immunoglobulin G (IgG), from a crude plasma protein fraction, which comprises preparing IgG supernatant by precipitating of a high portion of non-IgG proteins, filtering the supernatant by means of an anion exchange resin and a cation exchange resin connected in series, washing out protein contaminants and eluting IgG, performing a dia/ultrafiltration on the IgG-containing eluate, inactivating viruses in the eluate, performing further filtration of the eluate by means of an anion exchange resin and subsequently a cation exchange resin, eluting contaminants and subsequently eluting IgG and performing dia/ultrafiltration on th
