A qualitative study documented the use of examples in connection with reflection-for-action by mathematics educators. This article focuses on the use of mathematical examples that were chosen or designed by the teachers during lesson planning. The data are drawn from a 3-year project intended to make educational research in mathematics more useful to teachers. The focus in the present article was on how teachers reflected about students' learning as they prepared lessons. Analysis of the data showed that reflection-for-action was an effective teacher practice and useful for increasing the quality of the content the teacher intended to cover in a teaching situation. However, at the beginning of the study the teachers could not provide a proper explanation of what reflection was about. Their reflections were limited to preparing for the lessons in relation to the actual curriculum in Sweden. During the study, the teachers' reflection-for-action improved as a consequence of using patterns of variation in designing examples connected to the object of learning.