Abstract: Various factors influencing the direct labelling of monoclonal antibody (McAb)3H11 with 188 Re are studied. By using the optimized procedure, the labelling yield higher than 95% and the content of colloidal 188 Re is less than 5%. The biodistribution of the 188 Re McAb 3H11 in gastric carcinoma bearing nude mice show that 188 Re is ingested in tumor selectively to some extent. Its clearance from tumor is slower than that from most of the other organs or tissues resulting increased ratios of 188 Re concentration in tumor to non tumor tissue(T/NT) with the lapse of time. It is excreted via kidneys.\;