This chapter describes the potential, benefits, and drawbacks of collecting diary data on Twitter. The authors describe the process they used to collect data on Twitter in a pilot diary study, and report the findings from that study. As part of the exploratory study, the authors tested a number of different methods by conducting six diary studies with small, nonprobability samples. Recruiting, screening, and coordinating with participants involved multiple steps and interfaces. Twitter diaries can work effectively for nearly anyone who knows how to use a computer or smartphone, but the diaries are especially suited for collecting data from people who are active Twitter users because Tweeting is already routine for them. In some studies, recruiting a convenience sample on Twitter would be acceptable, especially when one is interested only in studying people on Twitter, or when conducting health interventions.