Statistical fatigue tests were conducted on structural carbon steel, S 45 C, in room air and in 3 % NaCl solution using three cantilever-type rotating bending fatigue testing machines which were specially manufactured for the purpose of the present study. Fatigue life distribution was examined at three stress levels in both environments, and twenty specimens were allocated to each stress level. In room air, it was found that fatigue life distributions followed the three-parameter Weibull distribution and were closely related to fracture morphology. In 3 %NaCl solution, they also followed the three-parameter Weibull distribution, but the shape parameter and the scatter in fatigue life were smaller than those in room air. It is suggested that the decrease in the scatter of fatigue life may be attributed to the small number of cycles to crack initiation in 3 %NaCl solution.