A body of literature has emerged suggesting that investors herd, or tend to make investment decisions on the basis of information provided by the trades of other market participants. In this paper, we use intraday data to examine whether traders herd during periods of extreme market movements using sector Exchange Traded Funds (ETFs). Two procedures, one based on identifying extreme up market and down market periods and the other based on incorporating a nonlinear term in a regression specification, are used to identify the possibility of the existence of herding behavior in nine sector ETFs traded on the American Stock Exchange. The results support the conclusion that investors do not herd during periods of extreme market movements using ETFs. Furthermore, we show that the market reaction to news is not symmetric for up markets and down markets.