Chapter headings. Mechanism of fatigue in the absence of defects and inclusions. Stress concentration. Notch effect and size effect. Effect of size and geometry of small defects on the fatigue limit. Effect of hardness HV on fatigue limits of materials containing defects, and fatigue limit prediction equations. Effects of nonmetallic inclusions on fatigue strength. Bearing steels. Spring steels. Tool steels : effect of carbides. Effects of shape and size of artificially introduced alumina particles on 1.5Ni-Cr- Mo (En24) steel. Nodular cast iron. Influence of Si-phase on fatigue properties of aluminium alloys. Ti alloys. Torsional fatigue. The mechanism of fatigue failure of steels in the ultralong life regime of N >107 cycles. Effect of surface roughness on fatigue strength.