A new kind of spatial task was devised to provide a description of the development of mnemonic strategy in early childhood. Five kinds of vertical arrays of drawings differing only in left-right orientation were presented one by one. Children at ages 5, 6, 7, and 9 years were asked to reconstruct the model. Most of the preschoolers succeeded only with those arrays in which drawings in the same orientation were juxtaposed. Memory for the most complicated array was not accurate enough until age 9. During the study, the oldest children usually verbalized the orientations as a sequence or the positions of the drawings in each orientation distinctively. This was interpreted as indicating that only the oldest children executed the sophisticated encoding strategies that integrate information on the orientation and position. Analysis of children's answers to the question about how to memorize revealed that awareness of using a strategy emerged at age 7 and grew clear by age 9.