As a result of the increased popularity of group-oriented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer tele- and videoconferencing. Regardless of the application environment, security services are necessary to provide communication privacy and integrity. This paper considers the problem of key agreement in dynamic peer groups. (Key agreement, especially in a group setting, is the stepping stone for all other security services.) Dynamic peer groups require not only initial key agreement (IKA) but also auxiliary key agreement (AKA) operations, such as member addition, member deletion, and group fusion. We discuss all group key agreement operations and present a concrete protocol suite, CLIQUES, which offers complete key agreement services. CLIQUES is based on multiparty extensions of the well-known Diffie-Hellman key exchange method. The protocols are efficient and provably secure against passive adversaries.