The Committee on In Vitro Tests of the American Academy of Allergy has collected a large pool of human serum containing high titers of total IgE for the purpose of establishing a U.S. reference material. This pool is free from hepatitis B surface antigen. The serum pool has been subaliquoted, lyophilized and tested for total IgE content. The paper radioimmunosorbent test (PRIST) technique was used for this measurement. All laboratories used the same lot of reagents. The Second International Reference Preparation was used as the reference standard in each assay. Multiple replicates of the pooled sera was tested for total IgE content with one set of reagents by each of the 14 participating committee laboratories. The results for total IgE content (IU) of the vials were: mean of means, 899; median of means, 901; weighted mean, 898; with an overall coefficient of variation of 15.3%. This new IgE reference material is available to all laboratories for use as a primary reference standard from the Research Resources Branch, NIAID-NIH, Bethesda, MD 20205.