Metastatic rates from subcutaneous xenografts in nude mice have been low possibly due to site of implantation. The applicant's approach is to use orthotopic onplanation of intact tissue specimens rather than cultured cell lines or dissociated tissue specimens. Results have indicated a high take rate (success in 4 of 7 patient cases) with direct onplanting to the colon in his laboratory where histologically-intact patient-colon-cancer tissue directly onplanted in the cecum or colon metastasizes regionally and to the liver. With regard to orthotopicity, the colon cancer tissue when grown subcutaneously, did not metastasize. In head and neck cancer a tumor implanted orthotopically in the muscles of the floor of the mouth grew invasively in the head and neck area whereas subcutaneous implants even in the head and neck area were encapsulated and not invasive. The orthotopic onplant method with intact tissue developed by the applicant allows extensive metastasis of a ras-transformed human bladder xenograft compared to injection of suspended cells into the bladder where no metastasis occurred. Onplanted human pancreatic tumors also grew orthotopically and spread regionally. The applicant proposes here to further develop the methodology for orthotopic growth and metastasis of colon, head and neck, bladder and pancreas carcinomas. Other methods to enhance orthotopic "takes" will include co-implantation of tumors with Matrigel, embryonic tissue and internal skin flap over the tumor on the target organ. He has also been able to transplant the orthotopically-growing colon tumors orthotopically to additional animals where they continue to grow orthotopically and metastasize with a 100 percent success rate for four serial passages. For one orthotopically-growing head and neck tumor, eight serial passages were carried out with a 100 percent success rate. This gives rise to the high probability of developing large cohorts of animals with orthotopically-growing human tumors for testing of new treatment strategies.