Iodine-bromine water from pit-hole of naphthalene layer was used in the daily water-bath treatment course of 22 rats within 10 days; after decapitation of these animals content of malonic dialdehyde and lipid hydroperoxides was estimated in homogenates of heart, lung, liver, kidney and spleen tissues. Simultaneous increase in the rate of lipoperoxidation was observed in the tissue homogenates of experimental animals. The treatment course with iodine-bromine water appears to activate the prostacyclin synthesis in vessel endothelium, thus suggesting the promising efficiency of the water in treatment of some blood rheology-related pathological states.