FORENSIC SEROLOGY IS A SUBFIELD OF FORENSIC SCIENCE AND INCLUDES ALL EXAMINATIONS OF BLOOD AND BODY FLUIDS IN CIVIL AND CRIMINAL CASES. THREE MAJOR ASPECTS OF FORENSIC SEROLOGY ARE THE IDENTIFICATION OF BLOOD AND BODY FLUIDS, ESPECIALLY IN CASES OF QUESTIONABLE STAINS, INDIVIDUALIZING BLOOD SAMPLES ONCE THEY HAVE BEEN IDENTIFIED BY USING SEROLOGICAL, BIOCHEMICAL, AND IMMUNOLOGICAL METHODS, AND BLOOD GROUPING TESTS IN CASES OF DISPUTED PARENTAGE. SPECIES TESTING OF BLOODSTAINS INVOLVES THE USE OF SPECIFIC ANTIBODIES TO HUMAN OR ANIMAL BLOOD IN ORDER TO PROVE THAT BLOODSTAINS ARE OF HUMAN ORIGIN. THE PRINCIPLES INVOLVED IN CATALYTIC TESTS AND CONFIRMATORY TESTS IN IDENTIFYING THE PRESENCE OF BLOOD IN STAINS ARE DESCRIBED. SPECIES TESTING OF BLOODSTAINS ARE CONDUCTED PRIMARILY TO DETERMINE WHETHER BLOODSTAINS ARE OF HUMAN ORIGIN. MORE SOPHISTICATED IMMUNOLOGICAL AND SEROLOGICAL TECHNIQUES MUST BE EMPLOYED IN SPECIAL CASES. INDIVIDUALIZING CHARACTERISTICS, OR 'GENETIC MARKERS' OF BLOOD ARE OF FOUR MAJOR CLASSES: 1) BLOOD GROUPS, 2) RED CELL ISOENZYMES, 3) SERUM GROUPS, AND 4) HEMOGLOBIN. EXAMPLES ARE PROVIDED OF THE USES OF GENETIC MARKERS TO DISTINGUISH AMONG VARIOUS PEOPLE INVOLVED IN CRIMINAL CASES. THE PROCEDURES FOR IDENTIFICATION OF SEMEN IN SEXUAL ASSAULT CASES IS ALSO DESCRIBED. ALTHOUGH IMMUNOLOGICAL TESTS FOR THE IDENTIFICATION OF HUMAN SEMEN ARE BASED ON THE SAME PRINCIPLES AS THE SPECIES TEST FOR BLOOD, IT IS NOT POSSIBLE TO OBTAIN AS GREAT A DEGREE OF INDIVIDUALIZATION WITH SEMEN BECAUSE OF THE FEWER GENETIC MARKERS IN SEMEN THAN IN BLOOD. REFERENCES ARE PROVIDED. (DEG)