Paleomagnetic orientation of in situ stress is one of the paleomagnetic services provided by Applied Paleomagnetics to clients in the petroleum and geotechnical industries around the world since 1986. Paleomagnetic orientation of in situ stress is integrated into our paleomagnetic core orientation service, which we first developed in 1982 for the U.S. Department of Energy's Multiwell (MWX) project in Mesaverde tight gas sands in the Piceance Basin, Colorado. Our paleomagnetic in situ stress orientation service can be used to predict the orientation of hydraulic fractures created for reservoir stimulation; plan optimum trajectories for deviated or horizontal wells; minimize wellbore instability, borehole breakouts, and lost circulation; determine whether open natural fractures will remain open during production; and plan optimum locations of injector and producer wells. In situ stress orientation can be determined in paleomagnetically oriented cores in two ways. First, in situ stress can be determined from the orientation of induced petal-centerline fractures induced in cores during the coring operation and striking parallel to in situ stress. Second, the in situ stress orientation can be determined in geomechanical test samples from core intervals that have been paleomagnetically oriented using our paleomagnetic core orientation service. Although rock mechanics laboratories perform a variety of techniques (ASR, DSA, SWAA, AAA) to measure geomechanical anisotropy and in situ stress orientation in cores, these reservoir anisotropy directions are misleading if the core samples have not been accurately oriented.