Case-control studies are important tools in modern epidemiological investigations of communicable disease outbreaks. The emerging pathogen, toxin producing Escherichia coli, has caused great awareness due to it's potential to cause severe and even fatal illness. To be able to take action against the spread of toxin producing E. coli a Nordic workshop was organised. The objectives of this workshop were: Exchange experience about the EHEC situation in the Nordic Countries. Learn from other countries about EHEC case-control studies, in order not to repeat any badly constructed questions. Discuss the methodology in case-control studies of sporadic cases. Establish a Nordic model of action for EHEC outbreaks or increased number of cases. To encourage co-operation between the Nordic countries in conducting case-control studies. Discuss how to proceed with the co-operation between the Nordic countries concerning EHEC case-control studies and outbreaks. This report summarizes the lectures given during the workshop and discussions. It is also included two examples of how a questionnaire could be designed.