A Fe35Co65 single crystal has been prepared by a long time anneal at temperature close to its fcc-bcc phase boundary. Its magnetostriction constant ë100 and magnetocrystalline anisotropy constant K1 was measured using a strain gauge rosette and magnetization and torque magnetometer curves. The magnetostriction constant ë100 is as high as 200 ppm. The value of the anisotropy constant K1 and the value of the susceptibility were small and influenced by the magnetoelastic energy. The symmetry of the torque curves changes from 2-fold to 4-fold with increasing external field which indicates the existence of a second uniaxial phase. This result can be interpreted by the alignment of the magnetization of an epitaxial fcc precipitate in the bcc host by external field.