The international workshop on "Promotion of Technical Harmonisation on Risk-Based Decision Making" reviewed the use of risk-based decision making across a range of industry sectors and countries. This paper presents the contribution to the workshop covering microbiological risk assessment of foods in international trade. The format is a response to a set of questions prepared by the organisers of the workshop covering the use and performance of risk assessment, evaluation of the acceptability of the risk and the use of risk assessment in the decision-making process (see "Preface" of this special issue). Risk Assessment of foods has been developed for chemical hazards rather than for microbiological ones. Acceptable or tolerable levels of food additives and contaminants have been included in many food standards worldwide. As part of the FAO/WHO Food Standards programme, the Codex Alimentarius Commission has issued many such standards, based on recommendations from two FAO/WHO expert bodies, the Joint FAO/WHO Expert Committee on Food Additives and Contaminants (JECFA) and the Joint FAO/WHO Meeting on Pesticide Residues (JMPR). This need to establish Food Standards on Risk Assessment procedures was reinforced by the signing of the Uruguay Round of Multilateral Trade Negotiations, presently known as WTO Agreements. The agreement on Sanitary and Phytosanitary (SPS) measures put particular emphasis on the establishment of acceptable or tolerable levels for microorganisms important. The SPS text specified that science and risk assessment should be the basis for the determination of the safety of food. Food safety standards issued by Codex Alimentarius were mentioned as the reference, and Codex was also the preferred international body to develop methods for their establishment.