Vanadium pentoxide exposure and its effect on select hematologic and chemical laboratory tests for workers exposed to 0.2-0.5 mg/m3 vanadium was studied. No association was found between vanadium exposure and the results of laboratory tests. The values of some chemical laboratory tests differed from those of controls. These findings, however, were not considered to be clinically significant because the mean values differed only slightly from each other. Hematologic tests showed no abnormalities when the concentration of vanadium in the factory air was 0.01-0.04 mg/m3.