In the detection of red-cell antigens in bloodstains by an elution technique, various concentrations of anti-A and anti-B monoclonal antibodies were investigated using bloodstains of groups A1, A2, B, and O to select a suitable dilution. No false positive reactions were obtained even when using the undiluted reagents. Also, the results demonstrated that not all reagents would be equally suitable for detecting the A antigen in A2 stains compared with A1 stains or stains that are older. In the use of an ELISHA technique to detect ABH substances in saliva and saliva stains, the study found that a comparison of the ELISHA technique with a currently used inhibition technique proved the ELISHA to be more sensitive when the same monoclonal reagents were used in each test system. In the detection of ABH antigens in bloodstains, a modification of the ELSIHA technique that did not require the extraction of the antigens from the bloodstains or their immobilization to the solid phase was developed. This apparently overcame some previously reported problems. Appended supplementary research reports