The influence of static mechanisms on fatigue crack propagation in Ti and Ti-V microalloyed steels is considered. Small inclusions originate void nucleation. In contrast, TiN coarse particles contribute to the formation of bursts of cleavage in the fatigue zone. Taking into account the microstructural characteristics of the matrix that surrounds the particle, the microcrack can be confined within the particle or propagate along the matrix forming a cleavage burst. The influence on macroscopic crack propagation of both types of static micromechanisms is considered. [S0094-4289(00)00902-6]