Abstract—Strain controlled continuous cycling fatigue tests are reported on three casts of Type 316 steel; the results obtained are shown to be consistent with published data.Strain controlled creep/fatigue tests are reported involving a hold period per cycle of between 0·2 and 168 h on one batch of Type 316 steel. An empirical extrapolation of the data and one involving a linear damage summation suggest that the existing Code Case N47 creep/fatigue design curve and rules are over‐conservative. A stress relaxation/fatigue endurance correlation shows some promise for predictive purposes. Although many of the mechanical test and metallurgical features observed are consistent with a fundamental crack growth extrapolation approach, further consideration of detailed aspects are necessary before it can be used with confidence. It is concluded that there are no entirely reliable methods of extrapolation currently available for Type 316 steel and longer term tests are therefore essential to reduce the extrapolation uncertain