Rotating bending fatigue tests of Ti added extra low carbon steel with no strain ageing were carried out. The results obtained are as follows; 1) At the stress of the fatigue limit, fatigue cracks did not propagate when N (number of repetitions) reaches 107. This was confirmed to the extent of N=8×107 in this experiment. That the strain ageing plays an important role in fatigue is well-known, but the above result shows that it is not always necessary for the non-propagation of fatigue cracks. 2) Apparent coaxing effect could not be observed in this experiment. Thus it is clear that strain ageing is an inevitable factor in the coaxing effect. Although propagation of crack tips become slightly harder during fatigue stressing, other regions are not reinforced to the crack initiation by strain ageing. Therefore new fatigue cracks initiate and propagate, resulting in failure, when the stress amplitude is increased.