Fatigue and creep crack propagation in 20 and 25% cold-worked Type 304 and 20% cold-worked Type 316 stainless steels were examined at 427 to 593°C (800 to 1100°F). The resistance to fatigue crack growth was slightly better for Type 304 stainless steel compared to Type 316 stainless steel, and was improved by an increase in cold work; however, these differences were small Compared to solution-annealed stainless steel, the cold-worked steels had higher crack growth resistance at high stress intensity levels. Creep crack growth occurred at 482°C (900°F), but much higher stress intensities, K, were required than in fatigue. However, at 593°C creep and fatigue crack growth occurred over the same K range and, in fact, at higher K levels crack growth in creep was faster than in fatigue. Retardation of crack growth was observed when the load on a specimen was changed from cyclic to static.