The identity of dislocations which contribute to plastic deformation of polycrystalline MoSi2when compressed at 1400°C has been determined using transmission electron microscopy. It has been confirmed that dislocations with Burgers vectors lying parallel to ⟨ 100 ⟩ and ⟨ 111 ⟩ are activated in response to the applied stress. In addition, the deformation microstructure is characterized by the presence of networks containing dislocations with Burgers vectors parallel to ⟨ 100], ⟨ 110] and ⟨ 111 ⟩. It has been shown that dislocations with Burgers vectors lying parallel to ⟨ 111 ⟩ are dissociated. A simple explanation has been developed to account for the occurrence of dissociation of particular dislocations, and on the basis of this model the dissociation is represented by