These papers are from the "International Symposium on New Microbiotests for Routine Toxicity Screening and Biomonitoring - Development - Applications - Cost-effectiveness" which was organized in June 1998 in Brno, Czech Republic. It comprises 60 original and peer-reviewed papers selected from over 100 oral and poster presentations given during this meeting by scientists from many countries worldwide. It features: overview of microscale bioassays with special emphasis on their application in various domains of environmental contamination; reviews on toxicity testing with microbiotests in a regulatory framework; description and application of microbiotests with lethal and sublethal test criteria, and of their sensitivity in comparison with conventional bioassays; reports on investigations with small-scale toxicity tests on natural waters, wastes, contaminated air, soils and sediments, specific chemicals and biotoxins; application of new microbiotests for mutagenicity and genotoxicity screening; and critical evaluation of the potential of specific microbiotests as alternatives to conventional toxicity tests.