The influence of the crystallographic variants of Ti3Ni4 particles on the cyclic stability of the high-temperature superelasticity of 〈001〉 -oriented Ti-51.5at.%Ni single crystals after stress-free and stress-assisted aging at 823 K for 1 h was investigated for the first time. After stress-assisted aging, the single crystals exhibited low cyclic stability of superelasticity (irreversible strain was 5.2 %, and critical stresses decreased by 14 %). After cycling, single dislocations and {115}B2 twins were observed, as a consequence of B2-B19′-B2 martensitic transformations. After stress-free aging, single crystals showed high cyclic stability: critical stresses were practically unchanged, and the irreversible strain did not exceed 0.2 %. No defects were found after cyclic testing; the stress-free aged crystals had the high strength properties of the B2-phase (2100 MPa) and B19′-martensite (>2700 MPa), in contrast to the stress-assisted aged single crystals, which had the strength properties of the B2-phase, 1630 MPa, and B19′-martensite, 1650 MPa.