Groundwater is an important medium for geochemical exploration of many different styles of mineralization, including porphyry copper, volcanogenic massive sulphide (VMS), sandstone uranium, and gold. Groundwater recharges to depth, resulting in greater likelihood of interacting with buried mineralization compared to surface geochemical methods, and thus providing a three-dimensional perspective. Advances in the understanding of ore formation processes, water-rock interaction and element transport/attenuation in the secondary environment are enhancing the efficacy of groundwater geochemical exploration. This paper describes key techniques and methodologies for sampling, analysis and interpretation of groundwater geochemical data, and provides two different approaches for use by industry: routine exploration and research approaches. New advances in analytical methods are providing new isotopic systems and improving the cost and speed of traditional isotopic techniques, which can greatly aid in interpretation of water sources, water-rock reactions and fingerprinting of ore sources. Case studies are presented for the use of groundwater geochemistry around a porphyry copper deposit in the hyperarid Atacama Desert of Chile, and VMS mineralization in a mature mining camp in Canada. This paper also summarizes key elemental associations for successful utilization of aqueous geochemistry in mineral exploration. The most successful aqueous-phase indicators of mineralization are those that are associated with the ore and are mobile in solution.