These reagents are found in various invertebrate species or isolated as crude extracts from seeds or other plant parts. After purification and characterization, lectins are versatile tools for identifying and grouping blood and other body fluids in the often contaminated stains found at crime scenes as well as in clinical settings. Applications of these reagents include human blood group antigens (with results extending to non-human blood group systems) and species determination and characterization. References delineate many novel uses of lectins in the area of forensic serology. 4 tables, 220 references. (Author abstract modified)