This paper presents the results of an experimental study of interfaces and dislocation substructures in a Nb-Ti base alloy subjected to creep deformation at different stress levels. Particular attention has been paid to the orientation relationship between the b.c.c. structure matrix and the f.c.c. structure precipitate. A specific orientation relationship, namely: [100]/(110)(M)parallel to[220](111)(P) (where M and P subscripts denote matrix and precipitate, respectively) was observed in the sample subjected to highest stress level. While the coincident site lattice model predicts a (100)/(100) -45degrees relationship, the orientation relationship developed is more consistent with lock-in and invariant line models. The implications of the observed relationship are discussed for the strengthening of the solid solution alloy.