The Supreme Court has agreed for a second time to hear Mayo v Prometheus, a case that tests the application of the In re Bilski ruling on patentable subject matter to diagnostic methods. Prometheus' patent specifically covers methods of determining the proper dosage of thiopurine drugs in patients. Following its decision in Bilski last year, the High Court immediately granted certiorari in the case and vacated and remanded the decision back to the Federal Circuit to reconsider the facts in light of Bilski. But in December last year, the Federal Circuit decided in favour of Prometheus for the second time, with little departure from its original reasoning. Mayo is now arguing that the Federal Circuit's decision is inconsistent with the Supreme Court's earlier precedents, with the reasoning of the three dissenting Justices in LabCorp v Metabolite and with Bilski. All eyes are on Justice Stephen Breyer, the remaining dissenter in LabCorp, who dubbed the diagnostic method patent at issue in that case "abstract" and "no more than an instruction to read some numbers in light of medical knowledge".