This paper analyzes the early exercise of exchange‐traded options by different classes of investors over the 1996 to 1999 period. A large number of exercises are identified as clearly irrational without invoking any model of market equilibrium. Customers of discount brokers and customers of fullservice brokers both engage in a significant number of irrational exercises while traders at large investment houses exhibit no irrational early exercise behavior. Rational and irrational exercise is triggered for discount and full‐service customers by the underlying stock price attaining its highest level over the past year and by high returns on the underlying stock.

We model the demand-pressure effect on prices when options cannot be perfectly hedged. The model shows that demand pressure in one option contract increases its price by an amount proportional to the variance of the unhedgeable part of the option. Similarly, the demand pressure increases the price of any other option by an amount proportional to the covariance of their unhedgeable parts.

This article uses a unique option data set to provide detailed descriptive statistics on the purchased and written open interest and open buy and sell volume of several classes of investors. We also show that volatility trading through straddles and strangles accounts for a small fraction of option trading volume and presents evidence that a large percentage of call writing is part of covered call positions. Finally, we find that during the stock market bubble of the late 1990s and early 2000 the least sophisticated investors in the data set substantially increased their purchases of calls on growth but not value stocks.

This paper investigates informed trading on stock volatility in the option market. We construct non‐market maker net demand for volatility from the trading volume of individual equity options and find that this demand is informative about the future realized volatility of underlying stocks. We also find that the impact of volatility demand on option prices is positive. More importantly, the price impact increases by 40% as informational asymmetry about stock volatility intensifies in the days leading up to earnings announcements and diminishes to its normal level soon after the volatility uncertainty is resolved.