The martensitic transformation and the defect density variation were studied during 500 thermal cycles of the Ti40.7Hf9.5Ni49.8-xCux shape memory alloys with various copper concentration (x = 1, 5 or 10 at. %). It was found that regardless the Cu content, the transformation temperatures decreased on thermal cycling. An increase in the Cu concentration led to alloys hardening but it did not improve thermal cycling stability. The variation in the defect density on thermal cycling did not correlate with the yield limit for dislocation slip measured in samples before cycling. The variation in the defect density variation did not correlate with the variation in the transformation temperatures on thermal cycling. This showed that the variation in defect density was not the only reason for the variation in the transformation temperatures on thermal cycling of cast Ti-Hf-Ni-Cu alloys