Longwall mining is conducted in bedded rock masses which are not only inhomogeneous but also transversely isotropic. Assuming isotropic rock mass properties can substantially under-estimate the impact longwall extraction can have on the redistribution of horizontal stresses. By invoking the transverse isotropic parameters derived from data on stress-relief roadways it is demonstrated that stress modifications can extend laterally 8 to 10 times the effective excavation height. For longwalls this may mean stress changes could extend up to a 1 km distance. Recognition of the role of transverse isotropy has implications to the understanding of stress concentration effects at the maingate/face corner and also predicting mining conditions in new longwall districts.