We analyze participation decisions in employee stock purchase plans. These plans allow employees to buy company stock at a discount from the market price and resell it immediately for a sure profit. Although an average employee stands to gain $3,079 annually, only 30% of individuals take advantage of this risk-free opportunity. Participation is more likely among employees who are familiar with stocks, are more educated, are less financially constrained, and make fewer errors in valuing financial securities. Our results suggest that compensation plans requiring active decisions by individuals can result in poor financial outcomes for employees of lower socioeconomic status.