The chemistry of the groundwater in Eastern Sterea Hellas (central Euboea and Asopos valley), central Greece, has revealed high concentrations of hexavalent chromium in groundwater systems exceeding, sometimes, the Greek and the EU drinking water maximum acceptable level for total chromium. The environmental impact of hexavalent chromium is a controversial issue critical to the protection of groundwater resources. By using the GFAAS for total chromium, diphenylcarbazide-Cr(VI) complex colorimetric method for hexavalent chromium, and flame-AAS and ICP-MS for other toxic elements, their concentrations were investigated in several groundwater samples. According to the results of this analytical work, the geochemical differences of those waters and the origin of the hexavalent chromium are discussed. The contamination of water by hexavalent chromium in central Euboea is mainly linked to natural processes, but there are cases that it is associated with anthropogenic activities. In Asopos valley the hexavalent chromium pollution is associated with the industrial wastes.