It is widely held that the professional athlete who is traded tends to perform better against the trading team than against other teams. Two psychological explanations for this hypothesis were advanced (a separation-hostility mechanism and an esteem loss-counteraction mechanism). Data were examined for 47 (30) professional baseball players over a 2-yr. (3-yr.) period. Support for the hypothesis was weak across the entire sample; however, some support appeared among players who (a) were traded for the first time, (b) had long tenure with the trading team, (c) were young, and (d) had high ability. Somewhat stronger positive results were found for individuals who met two or more of the conditions favorable to the hypothesis. As predicted, results attenuated over time.