During a 6-month period approximately 20% of the 589 patients admitted to the Maryland Institute for Emergency Medical Services Systems (MIEMSS), and who did not die, stayed less than 48 hours. About two thirds of these short-stay admissions (13% of the total number of admissions during the study period) were judged inappropriate on clinical grounds. This percentage is lower than the inappropriate rate (20%) experienced at areawide trauma centers in Maryland and may approximate the lower limit of the rate of inappropriate admissions due to unavoidable errors in triage. The inappropriately admitted patients did not impose a large fiscal or service drain on MIEMSS and did not interfere with the care of patients with more serious problems.