Secure and reliable group communication is an active area of research. Its popularity is fueled by the growing importance of group-oriented and collaborative applications. The central research challenge is secure and efficient group key management. While centralized methods are often appropriate for key distribution in large multicast-style groups, many collaborative group settings require distributed key agreement techniques. This work investigates a novel group key agreement approach which blends key trees with Diffie-Hellman key exchange. It yields a secure protocol suite called Tree-based Group Diffie-Hellman (TGDH) that is both simple and fault-tolerant. Moreover, the efficiency of TGDH appreciably surpasses that of prior art.