This technology assessment examines systems that are implanted in the brain or worn on the head that let people control electronic devices using brain signals. In clinical trials, these brain-computer interfaces helped people with severe disabilities. Businesses are also investing in developing the technology for entertainment and other uses. We identified challenges with this fast-moving technology. These include uncertainty over who owns sensitive brain data, how to support people with implanted devices over the long term, and what Medicare and private insurers will cover. We outlined policy options to help address these issues and more.