A metallurgical investigation was undertaken to identify the factors that are responsible for sensitivity to sulfide-stress cracking (SSC) in the heat-affected zone (HAZ) of microalloyed high-strength line-pipe steels, when the HAZ does not contain regions of high hardness. Sustained-load tests were conducted in the NACE laboratory sour-gas environment to determine the regions in which SSC initiated, and thereby to identify which regions were most sensitive to SSC.