The mechanical behaviour of three Nb-Al-V alloys with nominal compositions Nb-10Al-20V, Nb-15Al-20V and Nb-25Al-40V (in at.%) have been investigated. Both conventional constant strain rate deformation and compressive creep tests have been performed and the deformation microstructures have been examined by transmission electron microscopy (TEM). At room temperature all three alloys deform by planar slip, with dislocation/particle interactions giving significant strengthening for the two phase alloys. Deformation at higher temperatures occurs by a combination of dislocation glide and climb processes, giving more homogeneous microstructures. All of the dislocations in the B2 phase of these alloys are uncoupled superpartial dislocations with b = 1/2 . The influence of dislocation/domain boundary interactions on the formation of slip bands and uncoupled superpartials is discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.