Reliable Distributed Computing with the Isis Toolkit presents technical results documenting various internal aspects of Isis along with less technical results illustrating how systems are used to develop closely coupled and fault-tolerant application environments. The text consists of 20 papers that document Isis and describe its important applications. The first section deals with the underlying ideas of the Isis system. The second section describes design alternatives, the Horus system, integrating security in a group-oriented distributed system, and high availability in a real-time system. The third section examines the protocols used in Isis and Horus. The last section contains user-contributed papers on Isis applications and tools.