The active forms of oxygen (AFA) participate in modulation of mediation processes in patients with systemic lupus erythematosus. A direct correlation of AFA with serotonin and kallikrein was noted, a reverse one with the inhibitory systems. Reactivity of AFA proved to be most marked in patients with lupus nephritis. The role of polymorphonuclear leukocytes in the activation of vasculo-thrombocytic hemostasis is discussed.