Objective: To examine the relationship between emergency department (ED) use and health status, psychological social factors, and continuity of primary care (COC) in a senior population of health maintenance organization (HMO) members. Methods: An observational study using survey data and two-year prospective administrative data in a sample of 11,338 seniors aged 65 and older enrolled in an HMO Medicare-risk product. The study used multinomial logistic regression to model relationships between biopsychosocial factors, COC, and ED utilization. Health status and social measures were collected by survey. Depression was measured using administrative data including ICD-9 codes for depression combined with the use of antidepressant medications. COC was calculated based on visits with a single primary care provider for patients with two or more primary care visits. Results: The mean study age was 73 years, 42% were male, 27% lived alone, 13% had a Charlson score of 2 or greater, and 29% of the population had ED use during the study period. Advanced age, male gender, higher Charlson score, poor/fair perceived health, higher medication use, falls within the prior six months, need for assistance with activities of daily living, and use of assistive device were all significantly related to both one ED visit and multiple ED visits. Depression, low social contact, living alone, bereavement in the prior six months, and low continuity of primary care were related to multiple ED visits. Conclusions: ED use of seniors is correlated with a complex of physical, health status, and psychosocial factors. Psychosocial factors and low continuity of primary care were strongly related to multiple ED visits. Interventions directed to ED use among seniors should include components that address these psychosocial issues and improve continuity in the provision of primary care, in addition to the management of chronic conditions and declining health status.