Fatigue crack growth behaviors such as the crack growth rate and crack closure were studied using medium carbon steel (S45C) and two phase stainless steel (SUS329J1) under various combinations of the negative stress ratio, R and the maximum stress relative to the yield strength, σmax/σy. The main results obtained are as follows;(1) In the range of intermediate fatigue crack growth rate, the crack growth rate, da/dN increased with a decrease of R and an increase of σmax/σy for both the carbon steel and the two phase stainless steel. In this case, it becomes clear quantitavely that the compresion stress in the load cycle relative to the yield strength, Sc/σy is a very important factor which dominates the crack opening level and consequently da/dN in the both materials.(2) In the range of low fatigue crack growth rate, however, the compression stress in the cycle, Sc caused da/dN to decrease for the carbon steel but to increase slightly for the two phase stainless steel. This is closely related to the fact that the oxide deposite forms easily on the fracture surfaces of the carbon steel but does not form on the stainless steel.