The Trends in International Mathematics and Science Study (TIMSS) is an international comparative study that measures trends in mathematics and science achievement at the 4th and 8th grades every 4 years. TIMSS is designed to align broadly with mathematics and science curricula in the participating education systems and, therefore, to reflect students' school-based learning. The United States has participated in every administration of TIMSS since its inception in 1995, and the study provides valuable information on how U.S. students compare to students around the world. As the 2019 TIMSS results show, the United States had higher average scores than most participating countries in both mathematics and science at both the 4th and 8th grades. However, in 2019, the United States had relatively large score gaps between the top- and bottom-performing students in both TIMSS subjects and grades. Looking at changes over time in mathematics at both grades 4 and 8, U.S. average scores have increased over the long term--with higher average scores in 2019 than in 1995--but show no significant changes between 2015 and 2019. The results in this web report present descriptive data on student achievement designed to provide useful information to a broad audience, including members of the general public. [The intended use of this PDF is to allow readers to easily print all report text; however, for optimal figure viewing, please view the web report. Cover title varies: "TIMSS 2019 U.S. Results." For the 2015 results, see "Highlights from TIMSS and TIMSS Advanced 2015: Mathematics and Science Achievement of U.S. Students in Grades 4 and 8 and in Advanced Courses at the End of High School in an International Context. NCES 2017-002" (ED570893).]