Bioleaching studies have been conducted to obtain bacteria having a high ability to dissolve copper from chalcopyrite. For these studies, samples of mine drainage water which contain high concentrations of copper or iron ions in several abandoned mines in Japan were used to inoculate enrichment cultures on 0.16 M ferrous iron in the absence of chalcopyrite concentrate. Afterwards, these were accumulated and supplied to shaking-flask bioleaching tests on chalcopyrite concentrate. Copper dissolution rates were measured in chalcopyrite leaching experiments and compared with those using cell-free ferrous/ferric media. The copper dissolution rate in ferrous sulphate medium was higher than that in ferric sulphate medium. Moreover, tests in the presence of bacteria showed even an higher copper dissolution rate.