Validation plays an important role in the design process of embedded systems. It is the only way to relate the requirements and specification of a design to the real, final system. It is further a mean to obtain objective quality metrics about a system in its target environment, and to gain confidence in the systems quality. The validation of embedded systems is challenging. For complex industrial products, about 50 percent of the complete design time is spent on validation. The validation of distributed embedded systems is even more complex since these systems introduce new challenges such as (i) unreliable wireless communication, (ii) the distributed nature of the system, (iii) limited resources, and (iv) limited infrastructure for inspecting the system.In this thesis we contribute towards an increased quality of the design of distributed embedded systems. Our research on validation strategies addresses the challenging problems that arise from the peculiarities of distributed embedded systems such as wireless sensor networks, recofigurable-, and wearable computers. The specific contributions are presented and discussed for different phases and levels of abstraction in the design and development process.