The capture cross section for annihilation of two threads with opposite Burgers vectors moving on orthogonal slip planes in a thin film is examined using a numerical model. The initial configurations of threads that lead to annihilation are mapped out for a range of applied film stresses. The area of the region of initial configurations that lead to annihilation at a given stress and thickness is the capture cross-section. The size of the capture cross-section is shown to be highly sensitive to the applied stress relative to the critical stress for dislocation motion imposed by the film thickness. (C) 2012 Elsevier B.V. All rights reserved.