The paper focuses on the use of modelling and simulation technology in the design and development of engineering projects. Using case studies, the authors examine the experiences of engineers and designers working with these tools. The paper provides insights into how this technology is reshaping the way engineers work and solve problems. Engineering design remains a highly uncertain activity and the costs of failure can be high. It was found that the use of modelling and simulation helps engineers to better understand physical properties and behaviour - quickly, cheaply and accurately - before they construct artefacts and systems. Such tools can help engineers 'learn-before-doing' and experiment with the integration of different technologies and components. Modelling and simulation helps build the 'design conversation' between contributors to an engineering project, including customers and regulators. It provides opportunities for feedback and learning and can promote open, interdisciplinary and collaborative working styles. These findings are related to existing literature on problem solving in engineering design and a future research agenda is proposed that examines the opportunities for and limitations of these technologies.