Objectives: This study aimed to determine which factors contribute to frequent visits at the emergency department (ED) and what proportion were inappropriate in comparison with nonfrequent visits.Methods: This study was a retrospective, case-control study comparing a random sample of frequent attenders and nonfrequent attenders, with details of their ED visits recorded over a 12-month duration. Frequent attenders were defined as patients with four or more visits during the study period.Results: In comparison with nonfrequent attenders (median age = 45.0 years, interquartile range [IQR] = 28.0 to 61.0 years), frequent attenders were older (median = 57.5 years, IQR = 34.0 to 74.8 years; p = 0.0003). They were also found to have more comorbidities, where 53.3% of frequent attenders had three or more chronic illnesses compared to 14% of nonfrequent attenders (p < 0.0001), and were often triaged to higher priority (more severe) classes (frequent 52.2% vs. nonfrequent 37.6%, p = 0.0004). Social issues such as bad debts (12.7%), heavy drinking (3.3%), and substance abuse (2.7%) were very low in frequent attenders compared to Western studies. Frequent attenders had a similar rate of appropriate visits to the ED as nonfrequent attenders (55.2% vs. 48.1%, p = 0.0892), but were more often triaged to P1 priority triage class (6.7% vs. 3.2%, p = 0.0014) and were more often admitted for further management compared to nonfrequent attenders (47.5% vs. 29.6%, p < 0.001). The majority of frequent attender visits were appropriate (55.2%), and of these, 81.1% resulted in admission. For the same number of patients, total visits made by frequent attenders ($174,247.60) cost four times as much as for nonfrequent attenders ($40,912.40). This represents a significant economic burden on the health care system.Conclusions: ED frequent attenders in Singapore were associated with higher age and presence of multiple comorbidities rather than with social causes of ED use. Even in integrated health systems, repeat ED visits are frequent and expensive, despite minimal social causes of acute care. EDs in aging populations must anticipate the influx of vulnerable, elderly patients and have in place interventional programs to care for them.ACADEMIC EMERGENCY MEDICINE 2015;22:1025-1033 by the Society for Academic Emergency Medicine C are at the emergency department (ED) is usually focused on acutely ill patients facing life-threatening conditions. Worldwide, EDs have faced problems of overcrowding, long patient wait times, and admission bed blocks related to increasing numbers of patients.1-7 ED visits in Singapore's seven public hospiFrom the Duke-NUS Graduate