The low temperature fracture behavior of prestressed notched bars has been studied. The fracture stress was generally below the prestress level due to the influence of reverse plastic flow at the notch tip on unloading. When reverse plastic flow was prevented, low temperature fracture occurred at stress levels in excess of the prestress level. The benefits of prestressing are interpreted in terms of the introduction of plastic zones rather than the influence of residual stresses. The influence of aging and higher strain rates on the fracture behavior of prestressed specimens is also studied.