Present day enterprises are confronted with a continuously changing environment. These changes are due to globalisation, new technologies, regulations, novel business models, et cetera. This requires enterprises to be flexible. At the same time, enterprises are required to comply with an increasing number of government regulations on transparency, financial man-agement, et cetera. Enterprises therefore need to transform themselves regularly to meet these new challenges, while senior management of these enterprises needs to make conscious deci-sions about the future design of “their” enterprise and the path to “get there”. Such transforma-tions may range from changes in value propositions and business processes, via changes to the information systems used to support the business processes, to changes of the underlying IT infrastructures.Practitioners and scholars suggest that in order to make such conscious (and well informed) decisions on the design of an enterprise, an engineering-like approach to the design of enter-prises is needed. This has led to the notion of enterprise engineering. Since most real world transformations are large, they need to be divided into smaller chunks, typically in terms of programs and projects. This raises the need for a coordination mechanism between these chunks to safeguard that these “chunks” all contribute towards the strategic goals set for the transformation as a whole. When using an engineering approach to enterprise transformation, it becomes paramount to assure that the projects and programs provide the results conform to the original design. Traditional project/programme management does not provide such coordination, as it focuses on typical project parameters such as budgets, resource use, deadlines, et cetera. As a result, projects are “invited” to conduct local optimisations within their own local parameters. As a consequence, the results of these projects may actually not contribute to (or even hamper) the overall transformation goals.It is the mission of the field of enterprise architecture to provide a coordination mechanism that looks beyond mere project parameters and focuses on the qualities of the result of the projects from the perspective of the strategic goal of an enterprise transformation. In the context of enterprise architecture, ample research has been conducted on different ele-ments, such as: architecture frameworks, modelling languages, model analysis, the construction of views reporting on different stakeholder concerns, et cetera. Each of these elements is a valuable component to set up an effective coordination mechanism for enterprise transforma-tions. However, how to combine these elements into an effective method support for architec-tural coordination of transformations, has not received much research attention yet.The challenge, which the ACET project aims to meet, is the development of a theoretically grounded methodology that is an effective means for architectural coordination of enterprise transformations. Due to the diversity of contexts and goals in enterprise transformation, this methodology needs to be systematically adaptable to the situation at hand. In doing so, the ACET project will primarily focus on the so-called Business-to-IT stack. In other words, the lay-ered series of aspects: business services, business processes, information processing, and the underlying IT infrastructure.