Law enforcement officers in the field encounter a large number of new and confusing street drugs, which has increased law enforcement agencies’ need for portable drug testing devices. The FTCoE study is intended to inform and guide agency administrators as they consider the need for and the purchase of these devices. The study discusses the benefits, limitations, and implementation considerations for the various portable drug testing technologies; compares how they work; provides case studies of their use; and contains a glossary, information on emerging technologies, and a comparison of product features. The opioid crisis and the increase in novel psychoactive substances available to drug users was the impetus for compiling this study. Without field testing substances encountered, officers in the field must use their own judgment as to whether to make an arrest. If they have access to portable drug testing devices, this assists officers in establishing probable cause for making an arrest when controlled substances are identified. Having such a testing device in the field also prevents citizens from undergoing the inconvenience, stress, and expense of being arrested for possessing a substance that is not illegal.