The processing of mail at penitentiary mailrooms is a detailed, labor-intensive operation. In addition to routine inspection and sorting, all penitentiary mail is screened for concealed drugs. To improve the drug screening process, the U.S. Department of Justice, Office of Justice Programs, National Institute of Justice sponsored an investigative effort to identify, evaluate, and demonstrate drug detection equipment and technologies. The goal was to improve the efficiency and effectiveness of the drug screening process for the Bureau of Prisons (BOP) Federal penitentiary mailrooms. This report documents the evaluation performed at the Thunder Mountain Evaluation Center in 2001, as well as results of preparatory testing. The drug detection systems evaluated fell within two general classes of technology: trace detection and bulk detection. The drugs chosen for investigation were marijuana, cocaine, heroin, methamphetamine, ecstasy, and LSD. The Mailroom Scenario Evaluation evaluated the performance of drug detection instruments and technologies while simulating a prison mailroom environment. Due to difficulties in handling most of the drugs of interest, only marijuana and cocaine were used in the scenario evaluation. The chief objectives of the scenario test and evaluation were to: (1) simulate the penitentiary mailroom environment and processes; (2) simulate receipt of a relatively few mail items containing drugs within an overall larger quantity of “clean” mail; and (3) determine the performance of each drug detection instrument or technology in detecting mail items containing drugs. The operational minimum detection level (OMDL) evaluation was conducted in 2001 for four of the systems under test (SUTs). These SUTs were off-the-shelf trace detection units of nearly identical configuration to the units used in the Mailroom Secenario Evaluation. The OMDL results were used to extrapolate results of marijuana and cocaine testing to those drugs not tested in the mailroom scenario evaluation. Conclusions drawn from the evaluations included: (1) items mailed through the postal system did not pick up any substantial amounts of drug contamination; (2) the chemical reagent spray technology did not perform well for the concealment conditions and quantities investigated; (3) the bulk detection system could see small amounts of drugs in individual and simple mail items when hidden in the seams or in the contents; and (4) the trace detection systems had high false alarm rates. Future evaluations will address how to best employ the instruments in a real world environment. Figures and Appendices A-B