The term speciation refers to element occurence in various chemical forms or species as well as to chemical investigation of these forms, including their isolation from the sample, separation, detection, determination, characterization or identification as individual chemical compounds. Individual element species can be defined not only as specific compounds, but also with respect to biological availability of individual species, their physico-chemical properties, binding of elements to sample phases, fractions or structural components, etc. The review is focused on analytical problems of speciation of As, Cd, Cr, Cu, Hg, Pb, Se, Sn and Zn in environmental and biological matrices. The applicability of diverse analytical approaches, such as hyphenated chromatographic-atomic spectrometric techniques or electrochemical methods, are discussed and illustrated by a number of practical examples.