We describe a method of analysis for nickel in serum and urine. After the sample (1 ml) has been subjected to acid digestion, Ni(II) is extracted into methylisobutylketone as a furildioximate complex, and is measured by electrothermal atomic absorption spectrometry. The method is more sensitive and more convenient than previous methods, and is less subject to nickel contamination because the digestion and extraction steps are performed in a single tube. Analytical recovery of Ni(II) (10 or 20 microng/liter) added to 20 specimens of serum or urine averaged 101% (range, 94 to 107). The following values (mean +/- SD) were obtained for nickel concentrations in specimens of serum and urine from 19 healthy adults living in central Connecticut: serum = 3.1 +/- 1.6 microng/liter; urine = 2.7 +/- 1.6 microng/liter. The method provides a practical means for monitoring occupational exposures of workers to nickel compounds.