The aim of this study was to determine the antioxidant potential of the serum and the level of lipid oxidation products in the sera of apparently healthy adult males. The "antioxidant power" of the serum, defined as the ability to reduce ferric ions by antioxidants from the serum (FRAP), was taken as the indicator of total antioxidation potential. The formation of lipid oxidation products was evaluated as thiobarbituric reactive species serum test (TBARS). The ferrous oxidation in xylenol orange version 2 (FOX2) assay coupled with triphenylphosphine was used for measurement of total sera hydroperoxides (ROOHs). The following biochemical variables were determined in the sera: aspartat aminotranspherase (AST), alanine aminotranspherase (ALT), gamma-glutamyl transpherase (GGT), bilirubin, glucose, creatinine, cholesterol, triglycerides and hemoglobin. Blood sera from apparently healthy subjects (166 adult males) were analyzed. Median age of study participants was 36 years (range 25-50 years). The X +/- SD sera FRAP level of the 166 apparently healthy adult males was 1047 +/- 131 micromol/L (779-1410 range). The X +/- SD level of sera TBARS was 1.2 +/- 0.3 micromol/L of the sera (0.5-2.2 range). Compared with the level of TBARS in the sera, the level of FOX2-ROOH was significantly higher The X +/- SD level of lipid hydroperoxides in the fresh sera, determined as FOX2, was 3.9 +/- 1.5 micromol/L of the sera (1.9-6.9 range). Observation of correlation between FRAP and determined biochemical variables in the sera have confirmed a statistically significant linear correlation between sera FRAP and bilirubin, hemoglobine, glucose, ALT and triglycerides (p < 0.05). The results of sera FRAP, TBARS and FOX2 levels can help in estimating the antioxidant status of humans. Significant correlation between the antioxidant power of blood serum and particular biochemical parameters indicates the complexity of defence mechanisms and various molecules involved in increasing the reduction power of the serum.