Oxygen free radicals are the final or intermediate products of many metabolic reactions. Of greatest significance to the organism are superoxide anion radical (O2-.), hydrogen peroxide (H2O2), hydroxyl radical (.OH), singlet oxygen (1O2) etc. A proper ratio between both production and breakdown of oxy-radicals is essential for the maintenance of a dynamic equilibrium of vital processes. The superoxide dismutases protect cells against toxic influence of the superoxide. In addition, some square-pyramidally pentacoordinated copper(II) complexes, derived from tridentate Schiff bases of the N-salicylideneaminoalcanoate type, show remarkable SOD-like activity. A selected set of complexes of this type have been tested: potassium [aqua-(N-salicylideneglutamato) cuprate] (L- and D,L-form), potassium [(isothiocyanato)-(N-salicylideneglycinato) cuprate], potassium [(isothiocyanato)-(N-salicylidene-D,L-alaninato) cuprate], potassium [(isothiocyanato)-(N-salicylidene-beta-alaninato) cuprate] and potassium [(isocyanato)-(N-salicylideneglycinato) cuprate]. Our results suggest that the copper complexes are not only antioxidants, but may also possess anti-inflammatory, cytostatic and radioprotective properties.