Lesional impairment of the brain and spinal cord is a serious and usually irreversible disorder. There is only a small chance of functionally significant compensation of lesions. Neurons and glia aremarked by theminimal regeneration. Though plasticity and adaptability represent important mechanisms, which can contribute to the compensation of structural and functional CNS disorders, irreversible structural and functional deficits may develop. Transplantation of various cells incl. neurons from fetal brain or transplantation of genetically modified cells was therefore proposed. Clear verification of this method by animal tests and by clinically controlled trials is a necessary condition. Its application is expected in atrophic-degenerative and vascular diseases of CNS, tumors, injuries, seizure, inflammatory and demyelinating diseases in which the replacement of neurons, glia and enhancement of their regeneration play the key role. Transplantation of embryonic stem cells, fetal neural cells, and haematopoietic stem cells introduced by stereotaxic, hematogenic or intrathecal procedure gets the attention. Bioethical problems and the possible contribution of this method based on experience with transplantation of fetal cells into basal ganglia of 3 patients with Parkinson´s disease and haematopoietic stem cell transplantation in multiple sclerosis (n 1) are discussed.

        Key words: bioethics, cell and gene therapy, CNS tumors, Parkinson´s disease, multiple sclerosis.