HuPBLSCID mice were used to explore how they would response to human tumor cells of 80llMLC.Living 80llMLC cells appeared to be fetal to the the mice due to the production of human TNF- The hupBL-SCID mice did not generate any noticeable amount of specific human immunoglobulin either by single immunization with living 801/MLC cells or by repeated immunization with irradiated 80llMLC cells. Our preliminary experiments with huPBL-SCID mice showed that such chimeras would be a very useful models for tumor immunological researches.