'Enthusiasm' is claimed to be one of the most important ingredients of effective teaching. It is assumed in the studies that enthusiasm is a well-defined behavioural state which can be recognized and reproduced. However, at closer inspection the term becomes elusive and several ions arise: Is enthusiasm a universally valid category or does it bear cultural and individual differentiation? And does it always lead to good teaching? If not, which aspects are central? This study was designed using a hybrid qualitative method which consisted of a mixture of three different methods: multiple-case studies, in-depth interviews and classroom observations.