The specific features of lipid peroxidation (LPO) and the activity of enzymatic antioxidants in the plasma and red blood cells of patients with acute appendicitis, phlegmons, and abscesses located in the soft tissues of the shin, hip, buttocks, shoulder, and forearm were comprehensively evaluated. In these diseases, the signs of evolving oxidative stress were revealed irrespective of the site of an acute inflammatory focus. Excess accumulation of LPO products was recorded with the inhibition of antioxidative defense components, including erythrocytic glutathione-dependent enzymes. The manifestations of antioxidant deficiency were accompanied by a reciprocal increase in the concentration of the antioxidative protein ceruloplasmin and increased with more severe inflammation. The signs of imbalance in the prooxidant/antioxidant defense system slightly normalized at discharge during clinical convalescence.