Near-threshold fatigue crack-growth behavior at room temperature for a duplex stainless steel weldments was investigated to evaluate the effect of load ratio, microstructural change, and residual stresses. Near-threshold fatigue crack propagation behavior is found to show a marked sensitivity to .alpha./.gamma. phase ratio, and little residual stress effects. Threshold values in the heat affected zones are higher than those of base metals and threshold values for crack growth decrease with increasing the load ratio in the base metals and weldments. The fractrographic features in base metals, weldments and heat affectred zones were discussed in terms mechanism of crack growth.