Seventy-six adult subjects, 48 males and 28 females, were given placebo or 200 micrograms Cr in the form of chromic chloride in a double-blind crossover study, with 3-month experimental periods, to determine basal serum Cr levels and the effects of Cr supplementation on serum Cr and related variables. Basal serum Cr determined by graphite furnace atomic absorption for all subjects was 0.13 +/- 0.02 ng/ml (mean +/- SEM), and increased significantly to 0.38 +/- 0.02 ng/ml following 3 months of Cr supplementation. There were no significant differences in the serum Cr values for males and females. Serum Cr 90 min following a glucose load (1 g per kg body wt) was not significantly different from fasting during either the placebo or Cr supplementation periods. These data demonstrate that serum Cr increased significantly following Cr supplementation and is a reflection of Cr intake, but serum Cr concentration, even that following a glucose load, does not appear to be a meaningful indicator of Cr status.