The goal of the work is to establish the reasons for the unsatisfactory results of ultrasonic control (USC) of forgings made of austenitic stainless steel 08Х18Н10Т (321) of responsible purpose and to provide the scientifically based recommendations for improving their quality. Comprehensive studies are conducted, which included analysis of chemical composition, study of macro- and microstructure of forgings by metallographic and electron-microscopy methods, testing for resistance to intergranular corrosion (IGC), determination of mechanical properties. As established, the forgings rejected by USС, in contrast to the suitable ones, are characterized by: the presence of areas of liquation and structural heterogeneity of the steel, increased content of δ-ferrite, anomalous different-grain microstructure with a grain size from No. 8 (15 μm) to No. 2 (700 μm), the presence of chromium carbides on the grain boundaries, local susceptibility to IGC. In the structure of the forging turned out to be suitable during ultrasonic testing, there is an increased content (> 65%) of special low-energy grain boundaries Σ3 in the theory of coincident-site lattices (GB Σ3 CSL) that indicates the complete completion of recrystallization of the deformed steel during the final heat treatment. Recommendations are developed and provided to the metallurgical enterprise on improving both the manufacturing technology and the structural and qualitative characteristics of forgings made of austenitic corrosion-resistant steels of industrial production.