On December 10, 2001, the U.S. Supreme Court issued an opinion that may have important long-run implications for U.S. agriculture. Ruling in J.E.M. Ag Supply, Inc. v. Pioneer Hi-Bred International, Inc., the Court held that plant seeds and plants themselves (both traditionally bred and produced by genetic engineering) are patentable under U.S. law. This opinion concerns a case that started when Pioneer Hi- Bred sued J.E.M. Agricultural Supply (doing business as Farm Advantage) for selling Pioneer hybrid corn seed without Pioneer’s authorization. Pioneer alleged that the seed in question was protected by a number of patents and that, as the patent holder, it had the right to decide how, and by whom, the seed was to be sold and/or used. J.E.M. Ag Supply’s defense, in a counter suit, argued that the patents claimed by Pioneer were invalid. Specifically, J.E.M. Ag Supply maintained that Congress had excluded plants from the subject matter of patents when it provided specialized protection for plants through the 1930 Plant Patent Act (for asexually reproduced plants) and the 1970 Plant Variety Protection Act for sexually reproduced plants. The Court disagreed with this line of defense and ruled in favor of Pioneer. Essentially, it held that the landmark 1980 U.S. Supreme Court decision in Diamond v. Chakrabarty (which established that biotechnology innovations could be patented) does in fact extend to plants. Whereas this interpretation has been standard at the U.S. Patent and Trademark Office since 1985, the explicit U.S. Supreme Court ruling removes any ambiguity and, as a result, the right to patent plants is now firmly entrenched in U.S. law. We can expect that patents increasingly will be used to assert intellectual property rights on plant varieties and cultivars, inbred lines and hybrids alike. To understand what difference that might make, some background is in order.