This paper attempts to combine descriptive and normative approaches to the study of argumantation. Starting from the insights of ancient rhetoric and dialectic (Aristotle, Cicero), New Rhetoric (Perelman and Olbrechts-Tyteca), the Pragma-Dialectic framework (Van Eemeren and Grootendorst) and the theory of fallacies developed by Woods and Walton, bias is defined as a lack of appropriate balance and critical doubt relative to a specific kind of argumentative discourse. More particularly, two main kinds of bias are distinguishable: global and local bias. The former consists in a neglection of global dimensions of the issue in question; the latter results from an incomplete and/or incorrect application of argument schemes. A sample of about 80 letters to the editor written 1991-1992, where the problem of political asylum in Austria and Germany is the central issue, is described and critically evaluated in relation to the argument schemes and strategies of verbalization which are used. Two specific letters are analyzed in some detail. Finally, some recommendations concerning the improvement of both the climate and the standards of political discussions are suggested (e.g. the widespread practice of 'semantic fights' with the aim of pushing through one's own use of political terms should be replaced by the use of (more) impartial terms).