Öz The essential nature of selenium as well as its toxicity depend on the concentration and the chemical forms in which this element is present in environmental and biological samples. Dissolved inorganic selenium can be found in natural waters and soils as selenides, selenite and selenate. Organoselenium compounds that may be present in air, soils and plants are volatile methylselenides, trimethylselenonium ion and several selenoamino acids. This review article intends to show some general ideas and important procedures used for speciation analysis of selenium in particular matrices such as water, air, soils and plants