An invention is patentable only if it is “nonobvious to a person having ordinary skill in the art.” This obviousness determination is prone to two types of errors: type I errors, which are patent rejections that should have been granted, and type II errors, which refer to granted patents that are actually invalid. Although such errors can occur at both the agency level and the court level, this note focuses on errors at the level of patent prosecution at the United States Patent and Trademark Office (PTO). The note proposes that the PTO, in order to clarify its policy position on obviousness issues long before courts have the opportunity to weigh in, should promulgate forward-looking obviousness guidance under its nonlegislative rulemaking authority. This would increase the determinateness of the obviousness doctrine, producing more uniform results and reducing the level of uncertainty and error in patent prosecution. Guidelines of this sort are feasible under the current regime of institutional authority and will withstand judicial challenges. Moreover, they would be particularly suitable for the field of emerging technology, in which legal guidance is the most lacking.