{103}⟨331⟩ slip is found to be activated in MoSi2single crystals by deformation along [001] in uniaxial compression at 1000°C. The {103} slip plane has been determined by slip trace analysis. Observations by transmission electron microscopy reveal the presence of screw dislocations with a Burgers vector of ½⟨331⟩. However, ½⟨331⟩ dislocations of mixed character lying along the ⟨ 010 ⟩ direction are observed to have decomposed into two other perfect dislocations by the energetically favourable reaction