The No Child Left Behind Act (2001) mandates determining what educational practices are demonstrated to be effective through rigorous scientific research. What types of evidence are recommended practices based on? The authors analyzed 304 citations accompanying prescriptive statements in 6 recent teacher education textbooks. Prescriptive statements implied that if teachers or students performed "A" practice, then "B" student outcome would be likely to occur. Citations were categorized as primary (qualitative, correlational/descriptive, intervention) or secondary (books, review articles, literature reviews, meta-analyses, or position papers) sources. A relatively small percentage (18) of sources were random assignment intervention studies, considered by some as the "gold standard," whereas 64% came from secondary sources. The authors discuss the issue of whether teacher education textbooks offer evidence-based practice as well as future directions for research. (Contains 3 tables.)