National Health Insurance (NHI) was introduced in Taiwan on March 1, 1995. To evaluate the Influence of NHI on the volume and severity of emergency department (ED) visits, a retrospective analysis was conducted. The results showed that NHI did not result in a substantial increase in ED volume (P > .05), but the severity as measured by triage nurses did increase (P < .01). There was no change in the number of admissions to the intensive care units of patients transferred from smaller hospitals, but its percentage significantly decreased (P < .05), which may be a result of the significant increase in the total number of interhospital transfers. It was hypothesized that the universal coverage and a copayment contributed to these changes.