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The author considers some peculiarities of fatigue crack propagation inmetals at the stages of its initiation and initial development, stable growth, and unstablegrowth that precedes final fracture. It is shown that at the stage of initial growth offatigue cracks, the stress state, nonlocalized fatigue damage that precedes initiation ofthe main fatigue crack, residual surface stresses, surface manufacturing and in-servicedefects, and contact interactions are factors which determine the crack paths. Stablegrowth of a fatigue crack is primarily determined by the stress-strain state of astructure as a whole and by the stress-strain state at the crack tip taking into account itsvariation due to crack propagation, which is evaluated by the criteria of fracturemechanics. Also considered are peculiarities of fatigue crack development incompressor blades of marine gas turbines. It is shown that for embrittled steels, forwhich the plane strain condition is met during fatigue crack propagation, final fractureoccurs at very small crack sizes. In this case, the characteristics of fatigue fracturetoughness are appreciably lower than the static values. The paper also considerspeculiarities of unstable fatigue crack propagation.