It is known that aging under load in Ti–51 at. % Ni polycrystals results in the change of microstructure in contrast to aging in a free state. In the grains oriented in the 〈111〉 direction, under tensile load, one crystallographic variant of dispersed Ti3Ni4 particles grows under applied tensile stress in the elastic range; without load, four variants of particles grow [1]. Consequently, using Ti–51 at. % Ni single crystals for experimental investigation of aging under load allows us to control the microstructure of crystals, to exclude the effect of boundary grains, and to study the dependence of the shape memory effect and superelasticity on the number of crystallographic variants of the particles. Earlier, we showed that aging without load in Ti–51 at. % Ni single crystals is accompanied by a precipitation of four variants of Ti–51 at. % Ni dispersed particles Ti3Ni4, which do not undergo martensitic transformations [2]. The aging of Ti–51 at. % Ni single crystals under tensile load in the 〈111〉 and 〈122〉 directions was supposed to result in the growth of one variant of particles, as was predicted theoretically [1]. In this study, the effect of the number of variants of dispersed particles on the shape memory effect and superelasticity in the B2−R−B19' martensitic transformation was determined in Ti–51 at. % Ni single crystals.