The objective of this study was to examine a novel profile: thiol-disulfide homeostasis in acute brucellosis. The study included 90 patients with acute brucellosis, and 27 healthy controls. Thiol-disulfide profile tests were analyzed by a recently developed method, and ceruloplasmin levels were determined. Native thiol levels were 256.72 +/- 48.20 mu mol/L in the acute brucellosis group and 461.13 +/- 45.37 mu mol/L in the healthy group, and total thiol levels were 298.58 +/- 51.78 mu mol/L in the acute brucellosis group and 504.83 +/- 51.05 mu mol/L in the healthy group (p < 0.001, for both). The disulfide/native thiol ratios and disulfide/total thiol ratios were significantly higher, and native thiol/total thiol ratios were significantly lower in patients with acute brucellosis than in the healthy controls (p < 0.001, for all ratios). There were either positive or negative relationships between ceruloplasmin levels and thiol-disulfide parameters. The thiol-disulfide homeostasis was impaired in acute brucellosis. The strong associations between thiol-disulfide parameters and a positive acute-phase reactant reflected the disruption of the balance between the antioxidant and oxidant systems. Since thiol groups act as anti-inflammatory mediators, the alteration in the thiol-disulfide homeostasis may be involved in brucellosis.