Chapter 1 of this thesis describes the biological distribution and biochemical significance of selenium. A review of the main methods used for the analysis of selenium in biological materials is given in Chapter 2. In Chapter 3, the use of a gold fibre electrode in an electrochemical flow cell is described for the anodic stripping voltammetry of selenium. The manufacture of the flow electrodes and the subsequent optimisation of the analytical procedure are described. Chapter 4 is concerned with the cathodic stripping voltammetry of Se(IV) at mercury-coated carbon fibre electrodes. The optimisation of the mercury film formation conditions and the stripping voltammetric methodology at such electrodes are described. The use of a flow injection hydride generation method of analysis and its involvement in an inter laboratory study are described in Chapter 5. The development of the system from an initial batch system is outlined. A critical overview of the methods described in this thesis in relation to the commonly used methods is given in Chapter 6.