This article describes a process of developing, implementing and evaluating a clinical ethics support service intervention with the goal of building up a context-sensitive structure of minimal clinical-ethics in an oncology department without prior clinical ethics structure. Scholars from different disciplines have called for an improvement in the evaluation of clinical ethics support services (CESS) for different reasons over several decades. However, while a lot has been said about the concepts and methodological challenges of evaluating CESS up to the present time, relatively few empirical studies have been carried out. The aim of this article is twofold. On the one hand, it describes a process of development, modifying and evaluating a CESS intervention as part of the ETHICO research project, using the approach of qualitative-formative evaluation. On the other hand, it provides a methodological analysis which specifies the contribution of qualitative empirical methods to the (formative) evaluation of CESS. We conclude with a consideration of the strengths and limitations of qualitative evaluation research with regards to the evaluation and development of context sensitive CESS. We further discuss our own approach in contrast to rather traditional consult or committee models.