This paper describes the development and evaluation of a sequential extraction scheme for application to soils, tills, and surficial sediments to elucidate the form(s) in which an element is held and hence to provide information as to its genesis. The operationally defined phases selected for extraction have been assigned the following categories: adsorbed/exchangeable/carbonate, þAEC'; amorphous Fe oxyhydroxide, þam Fe ox'; crystalline Fe oxide, þcry Fe ox'; sulphides and organics; and residual, mainly silicates. Particular attention has been paid to the specificity of the hydroxylamine reagent, 0.25 M NH2OH.HCl in 0.25 M HCl, for extraction of the þam Fe ox' phase, well recognized for its scavenging properties of trace metals in the surficial environment. A decrease in the acid strength to 0.05 M HCl in this leach lessens the solubility of sphalerite and galena to <1% but a major portion of the humate and fulvate component in a sediment is dissolved, regardless of HCl concentration. Other reagents used in this scheme comprise: 1 M CH3COONa for þAEC'; 1 M NH2OH.HCl in 25% CH3COOH for þcry Fe ox'; KClO3/HCl followed by HNO3 for sulphides and organics; and finally HF-HClO4-HNO3-HCl for the residual minerals. Typical long-term precision values are provided in the data obtained by replicate application of these five leaches to the international standard reference materials TILL-1, TILL-2, TILL-3, TILL-4, and LKSD-4, for the elements Zn, Cu, Pb, Ni, Co, Mn, and Fe.