BLOOD STAINS UP TO 24 YEARS OLD WERE AVAILABLE FOR ANALYSIS. STAINS 8 YEARS OLD OR MORE WERE ON FILTER PAPER, AND MORE RECENT STAINS WERE MADE ON CLEAN WHITE COTTON CLOTH. VARYING AMOUNTS OF STAINED THREAD WERE EXTRACTED IN 4 DROPS OF 5-PERCENT AMMONIA IN A FLAT-BOTTOMED MICROTITER PLATE FOR ABO TYPING AT ROOM TEMPERATURE. AFTER 1 HOUR THE THREAD WAS REMOVED, AND THE EXTRACT WAS DISTRIBUTED IN 3 WELLS OF THE MICROTITER PLATE FOR A, B, AND H TESTING. THE EFFECT OF STAIN AGE ON THE ABILITY TO PERFORM ABO TYPING WAS INVESTIGATED IN STAINS UP TO 24 YEARS OLD. EXTRACTS FROM A SMALL LENGTH OF THREAD WERE USED FOR GM AND KM TYPING. THE ONLY VARIATION IN TECHNIQUE WAS THAT, AT THE READING STAGE AFTER MICROSCOPIC READING, PLATES WERE STOOD ON A SLOPING FRONTED LIGHT BOX AND READ USING THE STREAK METHOD. A TOTAL OF 56 STAINS, ALL ABOUT 2 MONTHS OLD, WERE TESTED SIMULTANEOUSLY ON THE SAME EXTRACT FOR ABO, GM, AND KM. THE USE OF MICROTITER PLATES IS ECONOMICAL IN THE TYPING OF BLOOD STAINS. SUCH TECHNIQUES NEED TO BE TESTED UNDER WORKING CONDITIONS IN AN OPERATIONAL FORENSIC SCIENCE LABORATORY. FURTHER WORK IS PLANNED TO USE MICROTITER TECHNIQUES FOR THE ABO TYPING OF SALIVA AND SEMEN AND FOR THE GM-KM TYPING OF SEMEN. SUPPORTING DATA AND REFERENCES ARE INCLUDED. (DEP)