The present paper reviews state of the art of theoretical and experimental studies of both the propagation and non-propagation of short fatigue cracks. The limitation of the conventional ΔK-based fracture mechanics approach to short crack growth is clarified, and several useful, alternative mechanical approaches proposed are discussed on the basis of crack growth mechanisms. The significance of short crack studies is emphasized in relation to fatigue-life prediction, fatigue-limit determination, and alloy microstructure design. Possible future developments are suggested.