The growth of dark line defects (DLD’s) has been observed in epitaxial AlGaAs wafers under optical pumping. The growth velocity as a function of optical intensity is given byV=AI1.8. In addition to recombination‐enhanced defect motion, stress‐induced dislocation glide is shown to contribute to the elongation of DLD’s in ⟨100⟩ and ⟨110⟩ directions. A climb mechanism may be responsible for the thickening of DLD’s after growth in ⟨100⟩ directions. The asymmetric growth of DLD’s between ⟨110⟩ and ⟨11¯0⟩ directions is attributed to the existence of &agr; and &bgr; dislocations and the absence of 90° rotational symmetry in the zinc‐blende structure.