THE HISTORICAL REVIEW REVEALS THAT IT WAS NOT UNTIL THE 1840'S THAT SCIENTISTS COULD RELIABLY IDENTIFY BLOOD AS BLOOD. EARLY TESTS WERE DESIGNED TO DETECT THE PEROXIDASE-LIKE ACTIVITY OF HEMOGLOBIN. IN 1901, A PROCEDURE FOR DISTINGUISHING HUMAN BLOOD FROM OTHER BLOOD WAS FOUND. AT ABOUT THE SAME TIME, THE ABO BLOOD GROUPINGS WERE DISCOVERED. THE M, N, AND P GROUPS WERE DISCOVERED IN 1927, FOLLOWED BY DISCOVERY OF THE RH FACTOR IN 1940. WORLD WAR II BROUGHT THE DISCOVERY OF A NUMBER OF NEW BLOOD-GROUPING SYSTEMS. ADVANCES IN BIOCHEMISTRY, GENETICS, AND IMMUNOLOGY CONTRIBUTED TO FURTHER ISOLATION OF GENETICALLY CONTROLLED SYSTEMS (E.G., HEMOGLOBINS, PLASMA PROTEINS, RED CELL ENZYMES) IN BLOOD AND OTHER BODY FLUIDS. SUCH SYSTEMS, OFTEN TERMED POLYMORPHISMS, HAVE REVOLUTIONIZED FORENSIC BLOOD GROUPING. SUMMARIES OF CHARACTERISTICS AND FORENSIC APPLICATIONS ARE PRESENTED FOR THE FOLLOWING BLOOD-GROUPING SYSTEMS: THE ABO SYSTEM (THE OLDEST ANB BEST KNOWN); THE MN SYSTEM (OFTEN USED IN DISPUTED PATERNITY STUDIES); THE RH SYSTEM; SIX DIFFERENT ENZYME POLYMORPHISMS; AND SERUM PROTEIN POLYMORPHISMS. SYSTEMS UNDER DEVELOPMENT ARE ALSO NOTED. ILLUSTRATIONS OF BLOOD ANALYSIS EQUIPMENT AND RESULTS ARE PROVIDED. A REVIEW OF THE GROWTH OF FORENSIC SCIENCE (PARTICULARLY FORENSIC SEROLOGY) IN CANADA IS INCLUDED, TOGETHER WITH A LIST OF REFERENCES. (LKM)