If there is enough stain material available Gm and InV factors can be proved to be present in semen. Contamination by nasal or vaginal secretions should be taken into account. Sweat, however, does not interfere with the determination. In saliva, InV but no Gm properties were demonstrable. Stamp glue reacts unspecifically with InV antiserum and could therefore be a source of error. The conclusive value of Gm and InV findings as evidence in court was derived from the phenotype frequencies obtained in blood samples of 400 unrelated persons.