A 29-year-old male welder reported systemic reactions after exposure to chromium. Inhalation challenge testing to 29 micrograms/m3 of sodium chromate aerosol resulted in late appearing systemic urticaria, angioedema, and severe bronchospasm that occurred at the same time as a threefold rise in plasma histamine. A direct leukocyte inhibitory factor test to 5.5 X 10(-6)mol/L Na2CrO4 was positive. Although the mechanism of this reaction is unknown, the positive leukocyte inhibitory factor and the general acceptance of hexavalent chromium as a contact skin sensitizer suggest that cell-mediated mechanisms could be involved.