Phase composition, structure, mechanical properties, and the characteristics of static and cyclic fracture resistances of high-strength maraging steels Fe-Ni-Cr-Co-Mo-Ti, Fe-Ni-Cr-Mo-Ti, and Fe-Ni-Co-Mo-Ti with retained and reverted austenites were studied. The specific features of deformation-related (strain-induced) γ→α transformation in the fracture zone were outlined, and the fracture surface characteristics after various treatments were examined. It was shown that the structural strength of maraging steels may be substantially improved by proving controlled contents of a metastable austenitic phase.