This paper describes the exercise behavior of over 50,000 employees who hold longterm options on employer stock at eight corporations. Employees typically exercise options years before expiration, commonly sacrificing half of the Black-Scholes value. Exercise is strongly associated with recent stock price movements, the market-to-strike ratio, proximity to vesting dates, time to maturity, volatility, and the employee's level within the company. These findings have implications for compensation planners, the FASB as it develops a new accounting standard for options, and financial statement users and preparers who apply and interpret the new FASB standard.