Seventy-two children (24 each from preschool, first, and third grades) were individually administered a structured interview assessing their belief in Santa Claus, as well as measures of causal reasoning and fantasy predisposition. Belief in Santa declined markedly with age. Level of causal reasoning increased with age and was related to decline in belief in Santa. Belief in Santa was unrelated to fantasy predisposition. Results were discussed within the framework of Gould's cognitive-affective theory of development which emphasizes the coexistence of several levels of cognitive maturity as the child learns to distinguish reality from make-believe.