Research on work aggression or anger has typically focused on supervisors and co-workers as the instigators of aggression; however, aggressive customers are also likely and may have unique consequences for the employee. We explore this phenomenon with a sample of 198 call center employees at two work sites. The employees reported that customer verbal aggression occurred 10 times a day, on average, though this varied by race and negative affectivity. Using LISREL, our data indicated that both the frequency and stress appraisal of customer aggression positively related to emotional exhaustion, and this burnout dimension mediated the relationship of stress appraisal with absences. Stress appraisal also influenced employees' emotion regulation strategies with their most recent hostile caller. Employees who felt more threatened by customer aggression used surface acting or vented emotions, while those who were less threatened used deep acting. Job autonomy helped explain who found these events more stressful, and implications of these results are discussed. Copyright © 2004 John Wiley & Sons, Ltd.