In this article we report about a study to assess Dutch teachers’ Pedagogical Content Knowledge (PCK), with special focus on programming as a topic in secondary school Informatics education. For this research, we developed an online research instrument: the Online Teacher PCK Analyser (OTPA). The results show that Dutch teachers’ PCK scores between low and medium. Also we enquired whether there is any relation between teachers’ PCK and the textbooks they use by comparing the results of this study with those of a previous one in which the PCK of textbooks was assessed. The results show that there is no strong relation. Finally, we looked for trends between teachers’ PCK and their educational backgrounds, as most of the Dutch teachers have a different background than Informatics. The results show that also in this case there is no strong relation.