The International Refinement Workshop and Formal Methods Pacific 1998 (IRW/FMP8) is a combined event. FMP8 itself incorporates the 4th New Zealand Formal Program Development Colloquium and the 7th Australasian Refinement Workshop. The international scope of the event is due to the welcome support of the British Computer Society specialist group in Formal Aspects of Computer Science, in lieu of their 1998 Refinement Workshop. IRW/FMP8 provides a forum for discussion of current research on mathematically based techniques for design and development of computer systems, especially formal or rigorous methods for developing executable programs from abstract specifications, tool support for formal software development, and practical experience with formal methods. Topics also include the specification and verification of hardware and software, and the specification and development of real-time, probabilistic, and concurrent problems. These proceedings present significant contributions to current research in formally developed computer systems.