A patented low-temperature polymerization method for methylmethacrylate (MMA) infiltrated bone marrow biopsies is described: it has been developed from our previous MMA technique and is a patented procedure. Differences from the previous method are (1) removal of stabilizer from the MMA monomer before its application, (2) the use of a different starter, (3) avoidance of O2 influence during polymerization by means of vacuum exchange with N2, and (4) polymerisation in a water bath to draw off residual heat. After this procedure, all immunohistochemical reactions are possible provided that the previous fixation is adequate. The effects of different fixatives are reviewed briefly without detailed analysis. Technically, this plastic embedding can be performed at least as rapidly as the classic paraffin embedding after decalcification. The advantages over the latter method are: (1) the cells can be better differentiated because semi-thin sections can be made; (2) the immunoreactions can also be performed on the basis of semithin sections, which means they can be interpreted more easily; (3) morphometric analyses yield more reliable results because of the constant thickness of sections; (4) osteological examination of bone trabeculae, especially the search for mineralisation deficiencies, is possible; (5) the plastic embedding procedure is less dependent on individual instabilities in the quality of performance of the staff members involved. Furthermore, it is worth mentioning that the costs for additional equipment necessary remain below DM 100,000 including an excellent microtome.