Purchase intentions are frequently measured and used by marketing managers as an input for decisions about new and existing products and services. Purchase intentions are correlated and predict future sales, but do so imperfectly. I review and summarize research on the relationship between purchase intentions and sales that has been conducted over the past 60 years. This review offers insights into how best to measure purchase intentions, how to forecast sales from purchase intentions measures, and why purchase intentions do not always translate into sales.