On January 26, 2001, the U.S. Patent & Trademark Office (PTO) stunned indigenous peoples of the Amazon Basin by rescinding its earlier decision to reject a patent on the “ayahuasca” vine that had been awarded to a California entrepreneur. Loren Miller won his U.S. Plant Patent 5,751 in 1986 after he purportedly discovered a “new and distinct” variety of ayahuasca (Banisteriopsis caapi) growing in a domestic garden in the Amazon rainforest. Varieties of ayahuasca (also called yagé) have been known and used for centuries by shamans of indigenous tribes throughout the Amazon Basin in religious and healing ceremonies to diagnose and treat illnesses, meet with spirits, and divine the future. Indigenous peoples have characterized the plant as a religious and cultural symbol analogous to the Christian cross or Eucharist. They were profoundly disturbed that anyone, particularly an outsider, could win private property rights over a sacred plant that they had known and cultivated since time immemorial. This issue brief analyzes the PTO’s decision to reinstate the ayahuasca patent. It reviews the arguments submitted to the PTO by Loren Miller and his attorneys, and concludes that the PTO erred on issues of fact and law when it agreed with Miller. The brief particularly criticizes the PTO in Part V for applying the legal test of a plant patent infringement case to the reexamination procedure, when the proper test for prosecuting a reexamination is whether the subject plant is patentable. The brief also calls attention to the blatant double standard the PTO applied in its treatment of Miller and the indigenous peoples and environmental organizations that initiated the reexamination.