We test for a “hot hand” (i.e., short-term predictability in performance) in Major League Baseball using panel data. We find strong evidence for its existence in all 10 statistical categories we consider. The magnitudes are significant; being “hot” corresponds to between one-half and one standard deviation in the distribution of player abilities. Our results are in notable contrast to the majority of the hot-hand literature, which has generally found either no hot hand or a very weak hot hand in sports, often employing basketball shooting data. We argue that this difference is attributable to endogenous defensive responses: basketball presents sufficient opportunity for transferring defensive resources to equate shooting probabilities across players, whereas baseball does not. We then develop a method to test whether baseball teams do respond appropriately to hot opponents. Our results suggest teams respond in a manner consistent with drawing correct inference about the magnitude of the hot hand except for a tendency to overreact to very recent performance (i.e., the last five attempts).