Iproplatin is prepared by treating cis-dichlorobis(isopropylamine)platinum (I) with hydrogen peroxide, mixing the product by N,N-dimetylacetamide at 5 C to give iproplatin-dimethylacetamide 1:1 addiction product (II). After elimination of N,N-dimethylacetamide by heating (II) at 50 C / 0.1 torr iproplatin is obtained.