This book constitutes the refereed proceedings of the 1999 Ada-Europe International Conference on Reliable Software Technologies, Ada-Europe '99, held in Santander, Spain in June 1999. The 36 revised full papers presented together with an invited contribution were carefully reviewed and selected from a large number of submissions. All current issues associated with the Ada programming language are addressed. The papers are organized in sections on Ravenscar profile and high-integrity systems, software architectures and design, testing, formal methods, education, distributed systems, real-time scheduling and kernels, tools, hardware/software codesign, fault-tolerance, and case studies.