This volume presents the proceedings of the Third International Symposium on Formal Techniques in Real-Time and Fault-Tolerant Systems held jointly with the Working Group Provably Correct Systems (ProCoS) at L?beck, Germany in September 1994. The book contains full versions of 5 invited talks and 33 carefully selected refereed contributions as well as 12 tool demonstrations. It documents that formal techniques constitute the foundation of a systematic design of real-time, fault-tolerant, and hybrid systems, throughout the whole engineering process, from the capture of requirements through specification, design, coding and compilation, right down to the hardware that embeds the system into its environment.