cis-Diamminedichloroplatinum(II) (cisplatin) is able to interact with human superoxide dismutase (hSOD1) in the disulfide oxidized apo form with a dissociation constant of 37 +/- 3 mu M through binding cysteine 111 (Cys111) located at the edge of the subunit interface. It also binds to Cu-2-Zn-2 and Zn-2-Zn-2 forms of hSOD1. Cisplatin inhibits aggregation of demetalated oxidized hSOD1, and it is further able to dissolve and monomerize oxidized hSOD1 oligomers in vitro and in cell, thus indicating its potential as a leading compound for amyotrophic lateral sclerosis.