Brain tissue from the cortex, midbrain (corpora quadrigemina ) or cerebellum was transplanted into the lateral ventricle or parenchyma of the right brain hemisphere of adult Wistar rats. Brain tissue transplants consisted of undifferentiated matrix cells and few neuroblasts. 30 and 110 days after operation transplants showed good development both in the lateral ventricle and inside parenchyma. They differentiated into organotypical and histotypical structures and cells similar to those formed in the normal development. Cortical structures developed from the cortex tissue, cerebellar structures from the cerebellum tissue, and nuclei white substance of corpora quadrigemina where formed from the midbrain tissue. Nerve and glial cells of transplants are well differentiated, tightly connected with the surrounding nervous tissue of the recipient, and remain viable by the end of the experiment. The immune response of the host to the transplant is not expressed. The behaviour of animals remains normal. The present experiments are the beginning of studies on grafting brain embryonal tissue to mammals with some nonhereditary and hereditary changes of the central nervous system (CNS) for our further investigations.