Requirements for the applicability of anion-selective electrodes in clinical analysis are discussed in terms of selectivity, response time, lifetime and stability. Basically, classical anion-exchangers, electrically charged carriers and electrically neutral carriers may be used as anion-selective components in solvent polymeric membranes. While classical ion-exchanger-based membrane electrodes are only of limited practical relevance, sensors containing ion carriers seem to bear a broad potential with regard to the feasibility of realizing the required properties. The control of the selectivity determining properties of electrically neutral tin organic anion carriers probably allows the development of sufficiently selective membranes for the assay of clinically relevant anions. Furthermore, the incorporation of membrane technology into the design of such carrier membranes may lead to fully optimized sensors.