1. There are three stages in the growth of a fatigue crack in a cylindrical specimen with a sharp annular notch: delayed, stable, and accelerated crack growth. At all stages, crack growth rate is higher, the larger the diameter of the specimens. 2. The rate of fatigue crack growth under the conditions described above depends in the stable section on the stress state created by the initial notch and the tip of the developed crack. It may be determined on the basis of an exponential dependence on specimen diameter and nominal stress. 3. Crack growth rate on the accelerated section is determined mainly by the stress state created close to the crack tip and may be computed from Paris' equation, in which the parameters n and C should be chosen with consideration of specimen dimensions and nominal stress. 4. The main reason for the substantial change in fatigue crack growth rate and the time of its growth with a change in specimen size is the dissimilarity in loads caused by different stress gradients for small and large specimens.