Sharp bends are observed in Shockley partial dislocations in a Cu + 15.6 at% Al alloy. Computations using the method of Head [1] suggest that these bends arise from unstable directions for Shockley partial dislocations in elastically anisotropic f.c.c. crystals. Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim