Metabonomic characterization of the effects caused by ozone and other stressors on normal human blood was performed. Samples of blood obtained from healthy subjects were treated ex vivo with increasing concentrations of ozone and/or with UV radiation and heat. (1)H-NMR analysis of plasma samples after treatments showed the quantitative variation of some metabolites and the formation of new metabolites normally absent. Both the increment of some metabolites like formate, acetoacetate, and acetate and the decrement of pyruvate were of particular interest. Moreover, the oxidation of ascorbic acid and the transformation of uric acid into allantoin after ozonation within the therapeutic concentration range were observed. In the ozonated spectra, 2 unidentified peaks appeared at 2.82 ppm and 8.08 ppm. They are related to the direct antioxidant activity of albumin in the presence of ozone and they could be considered as specific markers of the blood ozonation.