Preschool children's knowledge of printed words and letters was studied longitudinally, in order to achieve a definition and an ordering of reading readiness activities. Middle-class children were tested to determine what they knew about print, they were given word learning and word recognition tasks, and their parents returned questionnaires which assessed their perceptions of their children's developing understanding of print. The results indicate that an appreciable knowledge of printed words and letters and ways to recognize words exists before children receive formal reading instruction. Additionally, because the children showed a uniformly similar order of acquisition of this knowledge, it was concluded that a hierarchy for reading readiness exists and can serve as a basis for definition, testing, and instruction. (Author)