Cr-Mo steels are preferred in the construction of high-temperature components because they possess excellent strength, toughness, and corrosion resistance relative to carbon steels and most low-alloy steels. This article discusses the composition and metallurgy of the heat-resistant Cr-Mo steels. It details the Charpy V-notch (CVN) toughness properties of Cr-Mo steels relevant to fatigue and fracture resistance. The fracture mechanics of Cr-Mo steels are reviewed. The article analyzes the characterization of low-cycle fatigue based on fatigue damage calculations. It concludes with information on fatigue crack growth and fatigue behavior of weldments.