Teacher educators' knowledge about metacognitive knowledge and developing expertise can provide for insights about teaching these "difficult" constructs. In this explorative study, six teacher educators' remarks regarding metacognitive knowledge and developing expertise were examined. The teacher educators filled in closed-ended and open-ended questions to describe their experiences. Also, everything else that came to their minds was written down by the researcher. In this way, in-depth information was obtained. The results showed that the teacher educators were familiar with metacognitive knowledge and developing expertise; however, they raised several conditions and restrictions regarding the teaching of these constructs. The results suggest that teaching experience is an important factor in the way possibilities and difficulties in the teaching of metacognitive knowledge and developing expertise are conceived. (Contains 1 figure and 2 tables.)