The Syrian hamster cheek pouch was evaluated as a convenient transplantation site for studies of estrogen-dependent uterine growth and morphogenesis. At one month of age, hosts were either ovariectomized (Ovex) or ovariectomized and estrogen implanted (Ovex+E2), and at the same time the uterus from a 7-day old untreated donor was transplanted into the host's right cheek pouch. Periodic inspection (by simple eversion of the pouch) revealed viable transplants in the majority of hosts for both groups, and clear evidence of estrogen-dependent transplant growth that continued for at least 9 months. At that time, weight of the transplanted uterus was comparable to that of a given host's own in situ uterus, but uteri at both sites weighed six to eightfold more in Ovex+E2 hosts than in Ovex hosts. Histological analysis also revealed similar degrees of endometrial atrophy in Ovex hosts and hypertrophy/hyperplasia in Ovex+E2 hosts for both in situ and transplanted uteri. Furthermore, while only scant and rudimentary endometrial glands developed in both in situ and transplanted uteri within Ovex hosts, uteri at both sites within the Ovex+E2 hosts were riddled with cystic glandular structures and exhibited marked leukocytic infiltration. These data demonstrate that neonatal uteri transplanted to the hamster cheek pouch will grow, differentiate and follow an endocrine-responsive morphogenetic program that is quantitatively and qualitatively consistent with that of the host's in situ uterus. Lastly, we were able to cleanly separate epithelium from the stroma of 5-day old hamster uteri, reassociate the two tissues in vitro, transplant the recombinants into cheek pouches of adult female hamsters and subsequently observe growth and maintenance of a generally normal uterine morphology and differentiated function.