Key establishment is the most fundamental cryptographic primitive in all kinds of applications where security is a concern. However, the nature of limited resources on sensor nodes restricts the use of conventional key management techniques in wireless sensor networks. Many researchers have conducted different techniques to propose different types of key distribution schemes. In this paper, we survey the existing solutions and describe the state-of-the-art techniques. We not only classify these proposals into location-independent key distribution schemes and location-dependent key distribution schemes but also provide a comparison table. We hope to attract more research attentions on this direction. Copyright © 2011 John Wiley & Sons, Ltd.