In presenting a brief history of EBP, it is traced to its origins in the field of medicine, where drugs must be proven safe and effective through trials before they can be sold to the public. In criminal justice, EBP emerged when researchers began questioning whether rehabilitation programs in which offenders were participating had any impact in reforming their criminal behavior. This eventually led to the U.S. Congress mandating comprehensive evaluations of the effectiveness of the Justice Department's grants, in order to determine whether the money was well spent. In discussing the nature of evidence, the powerpoint presentation focuses on the use of scientific methods for collecting, analyzing and interpreting data that reliably show the effects of the program on participants' attitudes and behaviors, with the prevention of reoffending usually being the measure of effectiveness. EBP research methods are discussed as the means of obtaining evidence, with attention to the random assignment of samples to treatment and control groups. The presentation promotes CrimeSolutions.gov as a source of information on EBPs, as well as the resources offered by various agencies within the Justice Department. The presentation concludes with a discussion of issues and challenges in replicating a model EBP in a new setting.