This study screened 111 semen samples and 66 saliva specimens. The results showed that the behavior of some monoclonals were unpredictable and often failed to detect the corresponding antigen in a number of the tested specimens. The suitability of the monoclonal reagents for detecting soluable blood group antigens was unpredictable by their behavior with red cell antigens. Therefore, care must be taken in the selection of monoclonal reagents for use in the detection of secreted blood group antigens as false negative results could be obtained. 7 tables, 2 notes, 16 references. (Author abstract modified)