This study examined the pedagogical content knowledge of experienced and novice chemical demonstrators. It specifically delineates the nature of the declarative knowledge associated with science teachers' pedagogical content knowledge. Science teachers who (1) teach abstract concepts in chemistry, (2) have a strong interest in using demonstrations as a science teaching strategy, and (3) have high and low levels of experience conducting chemical demonstrations participated in the study. Clinical interviews were used to probe teachers' pedagogical content knowledge. The findings suggest that the experienced chemical demonstrators possess a greater representational and adaptational repertoire for teaching fundamental concepts in chemistry than novices. They also appeared to be more cognizant of the complexity of chemical demonstrations, how these complexities may interfere with learning, and how simplified variations of chemical demonstrations can promote concept learning. The implications for teacher education programs are discussed.