Slip asymmetry is a common occurrence in some monatomic crystals where it is due to complex core structures or specific packing of slip planes. Here we present another mechanism, based on molecular steric hindrance, which leads to asymmetric dislocation motion in cyclotrimethylenetrinitramine (RDX) molecular crystal. Dislocations move at different critical stresses when shear is applied in the positive and negative directions of the Burgers vector in the slip system that contributes most to plastic deformation. (C) 2013 Elsevier B.V. All rights reserved.