Experimental evaluations were conducted to examine the grain growth of the beta phase in investment cast Ti-6Al-4V as a function of time and temperature.  These data were then used as input to the subsequent development of a model that would allow the prediction of grain size in titanium castings, based on the  thermal history of the casting during solidification. Using Procast to model thermal history, validation of the grain growth model was conducted using an investment cast step block.  Prior studies have shown a relationship between the beta grain size in titanium and the tensile properties of the casting.  The availability of a model to predict grain size will enhance the prediction of tensile properties in titanium casitngs during the early stages of design.