This paper examines sixth-grade children's thinking related to solving ratio and proportion problems before these children had received any instruction in the domain. It explores unitizing and norming, one of the processes identified by both content analyses (Behr, Harel, Post, & Lesh, 1990); Harel, Behr, Post & Lesh, 1990) and research in children's thinking (Steffe, 1990; Lamon, 1989) as a possible approach for improving a mechanism for the growth of mathematical thinking. Children's use of this approach for ratio and proportion problems was examined and the results analyzed as a counterpoint to development of units in both the additive and multiplicative conceptual fields. The study indicated that children came into instruction in ratio and proportion with some informal understanding. While none of the children used symbols to represent their thinking, their conceptual competency exceeded their symbolic competency. Successful student strategies consistently involved a strong intuitive application of unitizing and norming. (KR)