The world's population is still growing up and asking for more and better food. High yielding plants with low external inputs should be the main aim of plant breeding to meet the higher demand for man and animal. Apart from traditional breeding plant biotechnology seems to have a certain potential to contribute to this objective. Safety and nutritional studies with such modified plants are the most important prerequisites for public acceptance of derived feed and food. The first step for safety and nutritional assessment of modified plants is the compositional analysis of potential food/feed and including the newly expressed proteins and other new constituents and the comparison with conventional counterparts. In vitro studies and experiments with laboratory animals are the next steps for assessments. Feeding studies with target animals are of special concern for nutritional assessment and are considered in more detail in the present paper.