Purpose: The purpose of this study was to compare the hospital length of stay in patients presenting to the emergency department (ED) with unspecified chest pain who were admitted through the ED to an inpatient bed prior to the initiation of the emergency department observation unit (EDOBS) and compare those patients admitted after the implementation of the EDOBS. Method: A retrospective, randomized descriptive study using chart review was performed at a large hospital system in the metropolitan Detroit region. Charts with an admission [International Classification of Diseases-9 Code 786.5, unspecified chest pain (n = 92)] were randomly selected. Results: For the inpatient group, ED registration time to unit was 6.4 hr and time from the unit to discharge was 80 hr (i.e., 3.3 days). For the EDOBS group, ED registration time to unit was 3.5 hr and time from EDOBS to discharge was 16 hr (i.e., 0.67 days). Length of stay decreased by 2.7 days overall. Conclusions: Using EDOBS for patients with unspecified chest pain provides for prompt and complete cardiac evaluation. Furthermore, the utilization of the emergency nurse practitioner helped alleviate the increased workload placed on the ED physicians in this type of unit. For example, the emergency nurse practitioner facilitated consults, reviewed diagnostic and laboratory findings (e.g., serial cardiac enzymes), and expedited hospital admission or discharge from the EDOBS. Study Limitations: Study limitations included a small random selection sample from one institution. Data collection was limited to review of the medical record and the accuracy of documentation. Key words: ED observation unit, ED nurse practitioner, length of stay, unspecified chest pain C HEST PAIN is one of the most common chief complaints of patients seen in emergency departments (EDs). The chief complaint of chest pain must be taken From ER-One, Incorporated, Professional Emergency Care, P.C., Livonia, Mich.