The purpose of this study was to examine young children's views about shadows. Young children hear references to or are involved in many scientific experiences in their everyday lives, and shadows are a part of children's everyday experiences. Young children may have constructed their knowledge about shadows through their daily experiences. Therefore, a total of 32 children, of which one-half were four years old and one-half were five years old, were individually interviewed twice to elicit their views and understanding of shadows. Data were collected by a mixture of picture-pointing, verbal explanation, and manipulation, and were analysed both quantitatively and qualitatively. We focused on five facets of children's ideas about shadows: ideas about the source of light, shadow orientation, shadow shape, shadow size, and shadow intensity. The five year olds performed significantly better on production of shadows, production of shadow shape, and production of shadow size, and also gave more reasonable explanations for their choices than did the four year olds, showing a better understanding of the concept of shadows. Another significant finding of the study was that young children have a much more sophisticated understanding of shadows than Piaget originally suggested and than their verbal explanations imply. (Contains 4 figures and 3 tables.)