The weak-beam method of transmission electron microscopy has been applied to measure the dissociation width of superlattice dislocations in Ni3(Al,Ti) as a function of temperature. Dislocations in thin foils parallel to (111) and (010) planes were investigated. No significant variation of the distance between the unit dislocations which constitute the superlattice dislocation was found over the temperature range from 298 to around 950 K. The experimental observations are discussed in the framework of the model proposed by Brown. It is based on the transformation of geometrical antiphase boundaries (APBs) into APBs in their thermodynamic equilibrium configuration. The role of this APB-based model is examined with respect to the anomalous increase of the flow stress with increasing temperature.