EACH LABORATORY RECEIVED TWO SAMPLES AND WERE ASKED TO DETERMINE WHETHER THE SAMPLES WERE HUMAN BLOOD AND WHETHER THE TWO SAMPLES COULD HAVE COME FROM THE SAME SOURCE. THE LABORATORIES WERE TO USE THEIR NORMAL PROCEDURES AND TO INDICATE THE METHODS OF ANALYSIS USED. THE SAMPLE SUPPLIER'S CHARACTERIZATION OF THE BLOOD SAMPLES, REFEREE LABORATORY RESULTS, AND TEST LABORATORY RESULTS AND METHODS OF ANALYSIS ARE REPORTED IN 13 TABLES, INCLUDING BREAKDOWNS OF RESPONSES FROM INDIVIDUAL LABORATORIES. ALTHOUGH TWO OF THE TABLES CONTAIN INDICATIONS OF RESPONSES THAT WERE INCONSISTENT WITH THE SUPPLIER'S STATEMENT, NO NARRATIVE INTERPRETATION OF THE FINDINGS IS PROVIDED. AN EXPLANATION OF SURVEY METHODS AND A COPY OF THE QUESTIONNAIRE ARE INCLUDED. THE RESULTS OF ANOTHER PROFICIENCY SURVEY INVOLVING BLOOD ANALYSIS ARE REPORTED IN NCJ-47524. OTHER PROFICIENCY SURVEYS ARE DOCUMENTED IN NCJ 47522-47523, 47525-47528, AND 47530-47542. (LKM)