he monoclonal antibody JH107,(McAbJH107)against human liver cancerwas labelled by the ch-T131 I-radiolabelling method. Its distribution andimage were detected in the nude mice bearing human liver cancer BEL-7402. Injecting 200 1 131 I-McAbJH107 to each mouse peritoneally the con-centrating of the radioactive substance at the site of the tumor began at24th and strengthened progressively, and reached its top at 96th. Theclearer image of tumor tissue was kept to 148th. At the same time,theradioactive background of the tissues around the tumor gradually disappea-red. In131I-NIgG of the control group well-distributed in the whole body,no significant concentration and no clear image were observed. At 48 and96th, T/NT mean values of 131I-McAbJH107 in normal tissues of 12 kinds(except the brain ) were 3.38 and 6.26 respectively, and ones of 131I-NIgGwere lower than 1.0