IgM can be used for several purposes such as early detection of certain diseases or, when labelled, localized cancer tumours. For their purification commonly chromatography is used. Methods for purifying such big molecules (M.w. around 950 kDa) are usually long and time consuming since these molecules have extremely low mobility therefore mass transfer between mobile and stationary phases is significantly reduced. When purified using affinity mode, serious decrease in IgM activity can occur because of long exposure to low pH in which they are unstable. Furthermore, because of their size, the IgM capacity of convenctional resins is rather low. CIM monoliths were already successfully used for fast separation of large molecules. In this work we tested applicability of anion-exchange CIM monolithic columns for preparation of IgM.