The contractor shall optimize the radioiodination reactions and test several difference radioiodinated conjugates for in vitro and in vivo stability. A comparison of a conventional (directly) radioiodinated antibody with the same antibody labeled using the radioiodinated conjugates, will be carried out. Studies using an iodine-131 labeled antibody will be conducted (in nude rats) to measure tissue dosimetry. The untimate goal of the study is to identify n antibody and a radioiodine conjugate that can become a commercial cancer therapy agent.