Case-control or cohort studies are important tools in modern investigations of food borne outbreaks. Epidemiological studies are one part of well-conducted investigations while the other part is microbiological investigation of suspected food items. However, in most of the food borne outbreaks, all food items are consumed or thrown away and the only way to reveal the causative food item is through conducting an epidemiological study.Epidemiological studies are also used in research to identify risk foods and/or risks behaviour in sporadic cases in order to gain more knowledge about transmission routes.This Nordic workshop dealt with methodological issues concerning case-control studies and food borne infections, both in the outbreak situation and with sporadic cases. The invited speakers were asked to take up methodological difficulties relevant to case-control studies. The participants in the workshop concluded that some "success stories" in food borne outbreak investigations would serve as good examples when planning how to deal with outbreak investigations. It was also concluded that this kind of workshop is most useful in terms of learning as well as giving support to each other.