<正> A sensitive and specific double-sandwich ELISA system utili-zing ascites fluid containing monoclonal antibody as a coatingantibody was developed for the detection of Clostridium botulinumtoxoid

toxin and artificially contaminated food specimens.Theminimal detectable amount（MDA）of toxoid varied from 4 to 31ng/ml.The lowest concentration for cross-reaction to botulinum AToxoid ranged from 4 to 8μg/ml.The specific index obtained wasbetween 250 and 1000.The MDA of botulin B was 16 ng/ml（4 LD50/ml）

whereas that of type A toxin was larger than 32 μg/ml（301LD50/ml）;the specific index was over 2000.The MDA of botulin Bin artificially contaminated food varied from 0.67 to 7.8 LD50/mland no cross-reaction was shown between types A and B.The ELISAsystem is close to RPHA in sensitivitv but is apparently superiorto the latter in specificity.