1. Theoretical Framework and Empirical Basis Lee Shulman (1986) coined the term pedagogical content knowledge as the crucial knowledge base of teachers. PCK is a specific form of knowledge of teaching which refers to the transformation of subject matter in the context of facilitating students' understanding. According to this model teachers need this type of knowledge to structure the contents of their lessons. Thus, PCK is a domain- specific knowledge. Unfortunately, Shulman did not mention how these elements of pedagogical and content knowledge were intertwined or used in the teaching practice. As little is known about how teacher deal with these issues, and how they develop their ability in this areas. Some empirical studies have been done, for example, in the USA or in England mostly in mathematics. So there is an importance of research on PCK. The PISA results do also emphasize the necessity of further research in the area of teachers' acting and beliefs, because these aspects might be a significant variable for the quality of the learning results. The objective of this study is to identify the PCK of VET teachers in the domain of industrial electrics/electronics occupations. The study follows the concept of method triangulation. The first approach was realised through a quantitative survey in 50 VET schools in 10 federal states (Bundesländer) in Germany. After this explorative study classroom observations with qualitative (narrative) interviews were done with 15 teachers in order to gain an in-depth sight of the acting and beliefs of VET teachers. 2. Preliminary Results of the Study In the German discussion it is assumed, that VET teachers are either experts of the discipline or pedagogues. The study shows, that both self-perceptions are intertwined depending on the point of questioning. Generally VET teachers say that they have a dominant pedagogical impetus. But asked about the most important knowledge base for teaching, however, the contents of the subject resp. the discipline (electrics/electronics) are mostly mentioned. So there is a mismatch between the teachers' beliefs resp. the self-perception and the acting in the classroom. This phenomenon can be illustrated with an example: The contents of the learning area electrical machines are usually taught by beginning with physical theories followed by specific aspects like the body of machines, modes of functioning, characteristic curves and variables. The only pedagogical aspect in a typical classroom situation is the didactical reduction of these contents from the scientific theory according to the learning group. Thus, the goal for a VET teacher is to structure this scientific knowledge in appropriate contents. With respect to the objective of VET, which should qualify the apprentices for working with these artefacts, a second mismatch can bee identified. For an expert worker in this field the use, installation, exchange or maintenance of electrical machines in drive systems are the relevant contents. But this work-related contents are not in the focus of the teaching practice. In contradiction to Shulman's model the study shows, that the knowledge base of VET teachers is predominately the curriculum knowledge, which is derived from the discipline, manifested in the curriculum and finally transformed in the teaching process. This does not mean that VET teachers do not have a broader knowledge base, but other knowledge categories are less relevant for teaching. The study is a contribution to the international discussion about the knowledge base of VET teachers demonstrated by the German situation in the domain of electronics. The paper also pays a contribution to the methodological requirements for investigating domain- specific knowledge.