The purpose of this study was to examine how children represent and compare number symbols. Pre-school, kindergarten, first, third, and fifth grade children and college students judged which of two visually presented digits was numerically larger. Twelve individuals were tested at each grade level. Response latencies were collected. Children at all levels were successful on the task. Results indicated that response latencies were a function of the ratio of the digit sizes; the larger the ratio, the faster the decision could be made. The children's performance demonstrated that: (1) they know the ordered sequence of the digits (the basis of the ordinal property of number); and (2) that numbers later in the sequence represent a greater quantity. This understanding of the quantitative basis of number is present even at an age when children do not understand the cardinal property of number symbols. It is argued that the ordinal number property and the understanding of the quantitative dimension which numbers represent form the psychological basis of the number concept. The results are discussed in terms of their relevance for early mathematics education. (Author/SB)