Extracellular superoxide dismutase (EC-SOD) variants having the superoxide dismutating property of the native EC-SOD and having a modified (reduced or increased) binding to heparin as compared to recombinant EC-SOD C as well as compositions comprising such variants. The EC-SOD variants are polypeptides comprising: 1) amino acids 1-193 of native EC-SOD C and 2) an amino acid sequence which is based on, but different from amino acid moieties 194-222 of recombinant EC-SOD C, either by being truncated or prolonged at the C-terminal end or by having substituted or otherwise modified one or more amino acid moieties of the sequence. Another EC-SOD variant is one which differs from recombinant EC-SOD C by being a glycosylation-free mutant. The variants may be produced by recombinant DNA techniques and are useful in the treatment of various diseases.