Measurement has been made of the corrosion fatigue short crack growth rate in a 12Cr steam turbine blade steel subjected to low frequency trapezoidal loading in aerated and deaerated 300ppb1All concentrations are specified in terms of ppb or ppm where these represent respectively parts per billion or parts per million by mass.1 Cl− and 300ppb SO42-, simulating early condensate chemistry. No difference in growth rate compared to that for long cracks was observed in deaerated solution but significantly enhanced growth rate was obtained in aerated solution for a short crack of length less than 250μm. Complementary stress corrosion cracking tests were conducted but to ensure crack development at modest applied stresses the environment adopted was aerated 35ppm Cl−, representing a severe system upset. In this case, the growth rate of the short crack was up to 20times higher than that for a long crack (>6mm), even though the crack length had reached 1.6mm. An explanation for both sets of data based on the difference in potential drop between a short and long crack is expounded.