The development process of car seats is very complex and many factors have to be considered in the development, such as anthropometry, physiology, safety, design and comfort. A factor making it more complex is the fact that future cars should be more sustainable, making the need for weight reduction more prominent. Improving comfort and at the same time reducing weight is a new challenge. Car seat research in the area of comfort is mainly focused on the decrease of discomfort. The most that can be achieved in this respect is that the person no longer notices the discomfort. Another possibility is to implement physiological knowledge in the seat research process, to increase the comfort and health in such a way that people will notice it. This is the chosen area of research in this PhD thesis. This knowledge can help car and seat manufacturers to address the issue of comfortable and healthy lightweight car seats and to stay ahead of the competition. Possibilities to improve comfort in this way studied in this thesis are a massage system an automatic seat surface adjustment resulting in an optimal pressure distribution, a head rest with special features for the neck, a new lumbar support and a special seat contour developement process.