Several recent investigations of children's cognition of musical pitch have examined the nature of children's sensitivity to the "tonal hierarchy" identified by Krumhansl (1990a). These studies presented children with musical "contexts," asking them to make judgments about subsequent pitches, and have produced strikingly divergent results. Factors of age and of type of "musical material used in context" appear to play significant roles in determining subjects' sensitivities. This paper describes two experiments that examine the time course of the development of children's cognitive representations of pitch relations, taking into account the contributions made to such representations by structural and by temporal factors (following West & Fryer, 1990). A probetone technique was used with two contrasting context types, one being a "typical" cadential sequence and the other consisting of different randomizations of the diatonic collection. This experiment was conducted on 285 children ranging between 6 and 11 years old, from two different single-sex schools. The results were further investigated in a gameplaying experiment—using chime bars— with children from each age group represented in the first experiment. These experiments appear to indicate that children's early representations of pitch relations are remarkably stable and that development may take the form of an increasing sensitivity to time-dependent characteristics of the musical surface leading to an internalization of the tonal hierarchy. Despite the different methodologies used here, results are broadly in line with those suggested by Krumhansl and Keil ( 1982), although children's representations of musical pitch as exhibited here appear to be more sophisticated than would be implied in that study.