In the experiment with 35-d head-down suspension of rats concentrations of lipid peroxidation (LPO) products and values of antioxidant defense (AOD) parameters were determined in the lever, skeletal muscles, myocardium, and blood plasma. In addition, activity of 11 plasma enzymes characteristics of these tissues was evaluated. LPO was found to be activated in the lever, myocardium and skeletal muscles in the first and 4-5 weeks of suspension. The period between weeks 2 and 4 marked phase variation of LPO intensity which could have baseline or increased values. Plasma LPO was inhibited due to AOD activation pointing to compensatory processes on the level of organism and absence of pathologies in the organs and tissues under study. As a rule, activity of the plasma enzymes directly or indirectly participating in energy metabolism was reduced. Enzymes-catalysts of other types of metabolism predominantly elevated activity during LPO intensification. Canonic analysis established a significant correlation of LPO, AOD and activity of plasma enzymes, and LPO and AOD in the rat's lever and plasma enzymes. These correlations between LPO, AOD and activity of diagnostically important enzymes can be used to diagnose and predict changes in the state of organism caused by simulated factors of space flight.