Tree squirrels are known to communicate with their tails, but the only aspects of this communication that have been studied are tail flicking and piloerection. We investigated the communicative significance of tail position in wild eastern gray squirrels (Sciurus carolinensis) by videotaping tails on squirrels at an artificial food source. We determined the relative dominance ranks of each individual in each video clip. Each time one squirrel approached another, we recorded the degree of aggression exhibited by the more dominant individual, as well as two variables describing tail position (tightness of curvature and portion of tail bent) for each squirrel. Both tail position variables and their interaction effects significantly predicted the dominant squirrel's degree of aggression in a multiple regression analysis, suggesting tail position communicates information related to aggression in eastern gray squirrels.