In Germany, appromaximately 5 million employees are exposed to biological substances (micro-organism in the broader sense) during their work in research, biotechnological production, food industry, agriculture, waste disposal and reprocessing os sewage as well as in health care. The development of a modern biotechnology and the change from conventional waste disposal to recycling recently became the focus of public attention. Due to this and other changes, more and more employees deal with biological substances and are partly exposed to considerable concentrations More than 200 experts from research, economy and occupational safety and health met at the symposium "Biological substances - new occupations and new legal basic conditions" and discussed new legal basic conditions and topical findings. The reorganization of legal basic conditions is to the fore, which results from the transfer of the EU-directive 90/679/EWG into the ordinance on protection of employees against hazards by biological substances (Ordinance on Biological Substances). Results of research projects are presented, which contain epidemiological and model-type occupational medical studies as well as issues on safety engineering. Projects on the assessment of workplaces, waste disposal and endotoxines are main focuses. Objective is the provision of information in order to eliminate still existing insecurity as regards the assessment of occupations with biological substances.