Subsurface Stress focuses on development of technologies to predict and assess geomechanical impacts of carbon dioxide (CO2) injection related to potential induced seismicity and to detect and analyze microseismic events should they occur. In situ stress is one of the key variables in predicting the geomechanical impacts, including potential induced seismicity, of pressure migration due to injection into a storage complex. In situ stress refers to the magnitude and direction of the stresses that exist in the subsurface before injection begins. Research is needed to reduce uncertainty in knowledge of the state of stress and resulting strains at potential storage sites and to improve the accuracy of tools and methods used to determine in situ stresses. Also, in many areas with potential storage opportunities, there is little existing data on in situ stresses, particularly in the basement. Subsurface Stress research includes the development of tools and methods to determine the subsurface state of stress, and geomechanical modeling to analyze the potential for slip-on fractures and faults and predict potential induced seismicity. In addition, tools and methods for acquisition, processing, modeling, and interpretation of microseismic events are being developed to continuously monitor CO2 storage sites.