The formation of fatgiue striations has been investigated by cycling oriented, cylindrical copper single crystals in torsion. Since in torsion of single crystals the applied stresses resolved on the slip systems vary as a function of azimuth, the stress on the cross‐slip system relative to that on the primary system varies with azimuthal position. The importance of cross slip to the formation of fatigue striations is tested by correlating the azimuthal position of fatigue striations with the stresses. It is concluded that a repeated cross slip mechanism will not account for fatigue striation formation.