Nutritional Epidemiology is a subdiscipline of epidemiology and provides specific knowledge to nutritional science. It provides data about the diet-disease relationships that is transformed by Public Health Nutrition into the practice of prevention. The specific contributions of nutritional epidemiology include dietary assessment, description of nutritional exposure and statistical modelling of the diet-disease relationship. Dietary assessment is moving away from the food frequency questionnaire as main dietary assessment instrument in large-scale epidemiological studies towards the use of short-term quantitative instruments due to the potential of gross measurement errors. Web-based instruments for self-administration are therefore evaluated of being able to replace the costly interviewer conducted 24-h-recalls. Much interest is also directed towards the technique of taking and analyzing photographs of all meals ingested, which might improve the dietary assessment in terms of precision.