ETAPS 2004 was the seventh instance of the European Joint Conferences on Theory and Practice of Software. ETAPS is an annual federated conference that was established in 1998 by combining a number of existing and new conferences. This year it comprised five conferences (FOSSACS, FASE, ESOP, CC, TACAS), 23 satellite workshops, 1 tutorial, and 7 invited lectures (not including those that are specific to the satellite events). The events that comprise ETAPS address various aspects of the system - velopment process, including specification, design, implementation, analysis and improvement. The languages, methodologies and tools that support these - tivities are all well within its scope. Different blends of theory and practice are represented, with an inclination towards theory with a practical motivation on the one hand and soundly based practice on the other. Many of the issues inv- ved in software design apply to systems in general, including hardware systems, and the emphasis on software is not intended to be exclusive.