th HESSD 2009 was the 7 IFIP WG 13.5 Working Conference in the series on Human Error, Safety and Systems Development which looks at integration of usability, human factors and human-computer interaction within system - th velopment. This edition was jointly organized with the 8 TAMODIA event on Tasks, Models and Diagrams for User Interface Development. There is an obvious synergy between the two previously separated events, as a rigorous, - gineering approach to user interface development can help in the prevention of human error and the maintenance of safety in critical interactive systems. Following the tradition of HESSD events, the papers in these proceedings address the problem of developing systems that support human interaction with complex, safety-critical applications. The last 30 years have seen a signi?cant reduction in the accident rates across many di?erent industries. Given these achievements, why do we need further research in this area? Recent accidents in a range of industries have increased concern over the design, management and control of safety-critical systems. Therefore, any system that involves human lives in its functioning is subject to safety-criticalaspects. Contributions such as the one by Holloway and Johnson (2004) report that over 80% of accidents in aeronautics are attributed to human error.