The Third International Mathematics and Science Study (TIMSS) is one of the most comprehensive international studies of schooling and students' achievement in science and mathematics. TIMSS was originally conducted in 1995. Four years later in 1999, the Third International Mathematics and Science Study-Repeat (TIMSS-R) was conducted. This document presents information on how U.S. eighth grade students performed in both studies and questions whether there have been any significant changes in achievement from an international perspective. Contents are divided into four chapters. Chapter 1 explains the importance of international comparison in education and the reasons for repeating TIMSS, identifies questions used and participating countries, discusses how the research was conducted, and presents the organization of the report. Chapter 2 discusses the mathematics and science achievement of the eighth grade students and presents student scores in both studies. Chapter 3 reviews issues related to curriculum and teaching, confidence levels of teachers, professional development, peer cooperation and classroom practices, and activities. Chapter 4 presents questions raised by the results of this report. (YDS)