The effect of stress history on stress corrosion cracking of E-4340 HR steel in an aqueous environment has been studied with the use of double-cantilever beam specimens. The stress history effect was found to influence the incubation time period with changes in the stress intensity. When the stress intensity was decreased, the incubation time period was dependent on the delta K and final K sub f during stress corrosion testing. When the stress intensity was increased, the incubation time period was independent of the applied stress intensity. However, the stress history effect did not influence the steady-state crack growth rates. In this report, the stress history effect is explained by using the hydrogen embrittlement mechanism.