1. Formation of σ-phase in high-temperature alloy KhN65VMTYu is governed to a considerable degree by its chemical composition. 2. Calculation of the chemical composition by the Phacomp method makes it possible to predict quite accurately the probability of σ-phase formation from the number of electron vacancies (Nv). For alloy KhN65VMTYu without iron and with 1–2% Fe, formation of σ-phase occurs with Nv≥2.30 and 2.20 respectively. 3. The σ-phase in alloy KhN65VMTYu has an acicular structure. No differences in σ-phase morphology were detected in cast, extruded, and forged metal. 4. There is most intense sigmatization in cast metal having a high degree of inhomogeneity. As structural homogeneity increases for the metal (cast → extruded → forget) the intensity of σ-phase formation decreases.