The USPTO Patent Trials and Appeal Board in Ex parte Michael Donovan et al. recently reversed the patent examiner’s rejection of claims in the medical diagnostic/prognostic arts on the ground of ineligible subject matter. This decision, issued two months after the USPTO issued its January 2019 Revised Patent Subject Matter Eligibility Guidance, and the implications for applicants seeking U.S. patents for medical diagnostic/prognostic technologies is discussed in this article.