Modern brain technology is a highly dynamic and innovative field of research with great potential for medical applications. Recent advances in recording neural signals from the brain by brain-machine interfacing presage new therapeutic options for paralyzed people by means of neural motor prostheses. This paper examines foreseeable ethical questions related to the research on brainmachine interfaces and their possible future applications. It identifies four major topics that need to be considered: first, the questions of personality and its possible alterations; second, responsibility and its possible constraints; third, therapeutic applications and their possible exceedance; and fourth, questions of research ethics that arise when progressing from animal experimentation to application to human subjects. This paper, in identifying and addressing the ethical questions raised by brain-machine interfaces, presents concerns that need to be considered if possible prosthetics based on modern brain technology are to be used cautiously and responsibly.