Sensor networks are widely used in a variety of commercial and military applications due to their self-organization characteristics and distributed nature. As a basic requirement for supporting security in sensor networks, key management plays an essential role in authentication and encryption. In this paper, we describe the hexagon-based key predistribution scheme and show that it can improve the effectiveness of key management in sensor networks. We show that this key management scheme can improve the probability of establishing pairwise keys between sensor nodes of up to two hops apart by more than 40% over other schemes. We also show that the security of a sensor network would decrease with the increase in sensor node deployment density or in signal propagation distance.