The federal government’s use of Other Transaction Authority (OTA) agreements has exploded in recent years, thanks in large part to a surge in popularity within the Department of Defense (DoD). Rather than a contract, grant, or cooperative agreement, OTAs are an acquisition approach that pursues innovation by enabling certain federal agencies to access goods and services outside of the traditional acquisition system. This CSIS report examines the notable trends in DoD OTA usage since the DoD's authority to enter into OTAs was expanded by the statuary changes in the FY 2015 and FY 2016 NDAAs. It seeks to provide insight into how the DoD is using OTAs to pursue innovation, how DoD spending under an OTA is organized, and to whom the majority of OTA obligations go.