Current guidelines for school-based substance use prevention suggest that prevention efforts should begin in elementary grades, before students begin using substances. Previous research suggests, however, that the use of evidence-based curricula in these grades may be low. Using a 2005 survey of public school districts in the United States that include elementary grades (n = 1563), we assessed the prevalence of elementary curricula use, particularly those designated as evidence-based. We found that although 72% of districts administer a substance use prevention curriculum to their elementary students, only about 35% are using one that is evidence-based and only about 14% are using an evidence-based curriculum more so than any other prevention curriculum. We present prevalence estimates for specific evidence-based curricula and conclude by discussing possible reasons for and implications of our findings. (Contains 1 table.)