Proceedings of an Advisory Group meeting, Vienna, 17–20 June 1985. The variations of sulphur isotopes in natural compounds (and of oxygen isotopes in sulphates) provide a powerful method of investigation in various fields of earth sciences such as hydrology, geochemistry, geothermal exploration, volcanology, oceanography, sedimentology, ore formation and environmental sciences. Contents: Summary; Isotopic composition of dissolved oceanic sulphate; Sulphur isotopes in the water of Lake Neusiedl, Austria; Relationships between the sulphur and oxygen isotope composition of dissolved sulphate; Sulphur and sulphate-oxygen isotopes in New Zealand geothermal systems and volcanic discharges; Isotopic composition and origin of sulphur compounds in groundwaters and brines in the Po Valley (northern Italy); Two case studies on the origin of aqueous sulphate in deep crystalline rocks; Sulphur and oxygen isotopic compositions of groundwater — and sabkha — sulphate in the Middle East; Radiolytic oxidation of sulphides and geochemical behaviour of sulphur isotopes in uranium deposits; On bias in 34S/32S data obtained in SO2 gas in mass spectrometry; Sulphur isotope analyses of trace sulphide and sulphate in various materials using Kiba reagent.