Cooperation between Queensland Government scientists and CRC CARE scientists from Southern Cross University has led to a successful National Demonstration Site for the Remediation of Acid Sulfate Soils in tropical northern Australia. This 775 ha site became highly degraded and acidified (pH’s <3 were common), following the construction of a large dyke through mangroves, installation of one-way floodgates, and an extensive drainage network to remove salt and grow sugar cane. The resulting and ongoing oxidation of acid sulfate soils caused severe soil and water acidification, failure of the agricultural enterprise, acid and metal discharges, and chronic fish kills in the adjacent Trinity Inlet. Conventional remediation by complete mixing of agricultural lime (CaCO3) with the acid sulfate soil was estimated to cost >A$300 million. Instead, a much lower-cost, controlled, lime-assisted tidal exchange technique was trialled and is largely managing and remediating the acid sulfate soils, as well as transforming the once degraded and acidified trial area into a flourishing tidal wetland system. The remaining areas are being similarly treated and detailed measurements are being conducted. The resulting science is increasing the understanding of the complex acid, iron and sulfur chemical hysteresis involved in trying to reverse the site’s extreme acidification.