In recent years the interest in preschool mathematics has increased. However, studies seldom focus on children under the age of three and research is scarce on the early use of mathematics observed in natural settings. This article reports a study of mathematical possibilities during diaper changing in a preschool setting. A diaper change can be a communicative moment when the child can experience mathematics with a professional preschool teacher, but it can also be a moment of mechanical routine with no pedagogical context. The intention of the study presented here was to investigate the mathematical potential preschool teachers described in relation to diaper changing and to examine the ways this potential was put into action. Both similarities and differences emerged regarding the mathematical potential preschool teachers described in relation to diaper changing and the mathematical content that they were observed to communicate. The results show that it is possible to communicate mathematical content in a pedagogical way during diaper changes, making this routine a learning opportunity for children. However, the results also show variations in the observed range and context of such communication, and therefore the potential for mathematical learning during diaper changes seems to differ widely. (author abstract)