Two separate methods were used to identify the most important historic airborne releases of radionuclides at the Idaho National Engineering and Environmental Laboratory (INEEL) with regard to potential human health impact. Both routine and episodic releases were evaluated. Although not specifically intended for an initial screening or ranking evaluation, particularly for episodic releases, the National Council on Radiation Protection and Measurements (NCRP) screening method was shown to be a valid method for providing a measure of the relative importance of both routine and episodic radionuclide releases, based on comparisons with the Radiological Safety Analysis Code (RSAC). For the work at the INEEL, a relative ranking procedure was used to identify the most important releases because a screening criterion (e.g., dose or risk value) against which the potential health impacts of the releases could be measured was not established. In addition, a precedent for a screening-level evaluation of episodic releases is lacking at this time. As a result, a ranking procedure was considered necessary because it was not clear that the NCRP method would provide screening-level dose estimates for episodic releases that could be defensibly compared to a screening criterion. To evaluate the NCRP method at the INEEL, routine operational releases were evaluated and ranked separately from episodic, or acute, releases because different assumptions and approaches were required to assess their potential importance. Based on comparisons with the RSAC method, the NCRP method may slightly underpredict the ingestion dose for episodic releases; however, using the NCRP screening method to identify the relative importance of release events, radionuclides, years, and facilities was shown to be valid and defensible for both routine and episodic releases. Because of the NCRP method's simplicity and relative ease of application, it provides a cost-effective and scientifically defensible way to make decisions and set priorities about decisions and directions in risk assessment.