The United States National Chemistry Olympiad (or USNCO) is a contest held by the American Chemical Society (ACS) used to select the four-student team that represents the United States at the International Chemistry Olympiad (IChO).
Each local ACS section selects, in whatever way it chooses, eight students (or more for larger ACS sections) to take the USNCO National Exam. One way to select these students is with the USNCO Local Exam, which is a significantly easier version of the National Exam consisting of 60 multiple choice questions. Thus, the first step on the path to the USA IChO team is usually the local exam.