Congestion affects the performance of a wireless sensor network in two aspects: increased data loss and reduced lifetime. All data generated in wireless sensor networks may not be alike; some data may be more important than others and hence may have different delivery requirements. As deployment sizes and data rates grow, congestion arises as a major problem in these networks. This congestion leads to indiscriminate dropping of data, i.e. data of high importance might be dropped while others of less importance are delivered. In this Book, I take a look at data delivery issues in the presence of Congestion Aware Routing Protocol designed earlier for wireless sensor networks. I propose a new data prioritization and a priority aware routing protocol - Advanced Congestion Aware Routing (ACAR) which slacking the packet dropping rate of data packets.