Debates about the future of school mathematics in the United States often centre on whether standards-based instruction in improving or undermining students' achievement. Critical for making progress in these debates is information about the actual nature of classroom practice in US classrooms. This article focuses on one key element of classroom practice teaching, and presents the results of two studies of randomly selected, nationally representative US eighth grade mathematics lessons that were videotaped as part of the TIMSS 1995 and 1999 video studies. Analyses compare features of teaching found in these lessons with pedagogical recommendations for middle school teachers in the Principles and Standards for School Mathematics (Principles and Standards) in order to examine the extent to which teaching in US eighth-grade classrooms is standards-based. Results show that typical mathematics teaching, in both 1995 and 1999, is more like the kind of traditional teaching reported for most of the past century than the kind of teaching promoted in Principles and Standards.