The agitation of a shear-thickening cornstarch-water slurry was studied. The objective was to predict the effect of dilatancy on agitation and the desired operational settings for agitating dilatant materials of known composition. Mixtures of cornstarch in water from 45–52 wt. % were agitated using different impeller types, impeller sizes, and vessel sizes (8–12 in. diameter). Torque and rotational velocity data were recorded for each configuration at various operational settings. The rheology of each mixture was characterized by a Brookfield DV-II+ viscometer, which confirmed shear-thickening behavior. The shear-thickening behavior of each agitated mixture culminated in a point of system instability, a certain impeller speed under a given configuration at which the shear-thickening mixture would start to seize up and the shaft and impeller would deflect substantially. It was under this condition that plots of rotational speed and shear rate versus impeller-to-tank diameter ratio were constructed from the recorded data. Agitation performance at unstable shearing conditions was found to be a function of the ratio between the impeller diameter and the tank diameter and was relatively independent of the tank diameter and impeller type. This suggests that operational limits to avoid unstable shear-thickening behavior upon scale-up are predictable. Furthermore, a relatively linear relationship between the impeller rotational speed and the diameter ratio was observed at the point of instability. This linearity may also have implications for the scaling up of shear-thickening agitation. Further testing should be carried out to confirm these results and to develop from them a size-independent empirical correlation that can assist in the scale-up of dilatant agitation systems to achieve optimum performance without instability.