The effects of surface properties of activated carbon (AC), pH and temperature of solution on Cr(VI) removal and reduction were investigated. AC oxidized by HNO₃ could possess large amount of surface functional groups and showed a higher Cr(VI) removal than AC with little amount of surface functional groups prepared by outgassing at 1000°C under neutral conditions. This result indicates that AC possessing the acidic functional groups had a reduction ability of Cr(VI). In contrast, under highly acidic conditions Cr(VI) was more easily reduced to Cr(III). The decrease amount of both adsorbents consequently showed the same value. The decrease amount increased with the increase in temperature. From the difference in reduction amount of Cr(VI) on AC which had different surface conditions, the carboxylic and/or carboxylate groups would be involved in the reduction process.