SUMMARY: Hypophysectomized red-spotted newts [Notophthalmus (Triturus, Diemictylus) viridescens viridescens Rafinesque] received autoplastic, homoplastic or xenoplastic grafts of pituitary glands beneath the lower jaw. Autografted animals, in accord with previous observations, survived indefinitely. Homografted animals had a mean survival time several times longer than either that of unimplanted, hypophysectomized animals or that of homografts of skin. No difference between rates of iodine turnover was found between thyroid glands of animals with homografts and animals with autografts but in both groups the rates of iodine turnover were lower than in intact controls. Great variation was found among the mean survival times of animals with xenografts. Newts with pituitary grafts from the frog, Rana pipiens, survived about as long as unimplanted hypophysectomized animals. Pituitary grafts from the salamander, Desmognathus monticola, apparently gave rise to some toxic reaction since their host newts died within short periods of time, yet newts with grafts from the mudpuppy, Necturus maculosus, lived longer than hypophysectomized control animals and some newts grafted with glands from a west coast newt, Taricha torosa, lived indefinitely.