It is generally agreed that approximately 1 in 10 hospitalized patients experiences an adverse event, and recent research has also quantified the daily risk of preventable adverse events for a typical hospitalization. The phenomenon of cascade iatrogenesis—a single patient suffering multiple adverse events—is well known to clinicians, and this study sought to quantify the incidence of this phenomenon. Using the AHRQ Patient Safety Indicators as a screening tool, the authors found that multiple patient safety events occurred in approximately 1 in 1000 adult hospitalizations. Although these instances were rare, patients with multiple adverse events had prolonged hospitalizations and significantly increased costs compared with uncomplicated hospital stays.