The Third International Mathematics and Science Study (TIMSS) 1999 Video Study is a follow-up and expansion of the TIMSS 1995 Video Study of mathematics teaching. Larger and more ambitious than the first, the 1999 study investigated eighth-grade science teaching as well as mathematics teaching, expanded the number of countries, and included more countries with relatively high achievement on TIMSS assessments in comparison to the United States. The results of the mathematics portion of the study are presented elsewhere (Hiebert et al. 2003). Discussion of the results from the 1995 Video Study can be found in Stigler et al. (1999) and Stigler and Hiebert (1999). This document highlights key findings from the science lessons and is based on the full report, Teaching Science in Five Countries: Results From the TIMSS 1999 Video Study (Roth et al. 2006).