The densification of titanium aluminide powders during hot isostatic pressing has been measured in situ by an eddy-current sensor. The samples were found to experience enhanced densification as they transformed from an initial metastable α2 structure to an equilibrium structure consisting mostly of the γ phase. The temperature at which the enhanced densification occurred corresponded closely to the temperature at which an exotherm is observed by differential thermal analysis. Evaluation of several possible explanations for this enhanced densification indicates that it is most probably the result of transformation plasticity. © 1992.