Indirect immunoperoxidase technique (IIP) has been employed for determination of IgG antibody titer to cytomegalovirus (CMV) in sera from 110 blood donors. Titers have been compared with complement fixation (CF) and indirect fluorescent antibody (IFA) technique titers, the latter being applied to determination of all specific antibody classes. Within variability range of the quality of reagents employed in different tests, it seems reasonable to conclude IIP technique is as sensitive as IFA and much more sensitive than CF test. Considering CF test is able to detect only IgG antibody, the advantage of using immunohistochemical techniques is obvious. Moreover IIP does not need fluorescence microscope and results reading is easier and can be delayed. Non-specific staining of Golgi area is shared by both techniques, but endpoint determination has to take into account only the nuclear virus-specific inclusion labelling.