The alignment of instruction with the content of standards and assessments is the key mediating variable separating the policy of standards-based reform (SBR) from the outcome of improved student achievement. Few studies have investigated SBR's effects on instructional alignment, and most have serious methodological limitations. This research uses content analyses of state standards and assessments and survey data on more than 27,000 teachers' instruction in mathematics, science, and English/language arts (ELA) to investigate changes in instructional alignment between 2003 and 2009. Fixed-effects models indicate that alignment in grades K-12 mathematics increased by approximately 0.19-0.65 standard deviations, depending on the grade and target. Alignment also increased to grades K-12 standards in ELA and grades 3-8 standards in science, though the magnitudes were smaller. Multiple alternative specifications support the findings of increased alignment. Implications for research and SBR policy are discussed. (Contains 6 tables and 1 figure.)