This review determined how many drug prevention curricula available to schools have been shown in rigorous research studies to reduce substance use behavior. Forty-seven curricula which met the following criteria were included: 1) they focused on primary prevention of alcohol and/or drug use, 2) they were classroom-based curricula designed for any grade level P-12, 3) they were nationally and currently available, and 4) program distributors were willing to provide samples of curriculum materials to determine drug abuse prevention content. Of the 47 drug abuse prevention curricula identified, 10 (21%) had been subjected to sufficiently rigorous evaluations. At least eight of the 10 programs have been shown effective at reducing tobacco or drug use, in at least some studies. The remaining two programs did not appear to have sustained effects on drug use, although they had variable success at reducing substance use early on. One of the 10 programs has been shown to have positive effects lasting into young adulthood. Six of the 10 curricula have been shown to have effects lasting for at least two years after the pretest. Two curricula have not been evaluated beyond the post-test, so it is impossible to know whether their effectiveness will last. Recommendations to increase the number of programs rigorously evaluated are offered.