This paper focuses on the identification of some conceptual factors underlying the initial learning of algebra. It describes a study which uncovered three predominant notions existing in a sample of ten 12- and 13-year olds prior to formal instruction in algebra, and the ways in which a particular approach to the teaching of algebra affected both the existing concepts and the construction of new ones. Analysis of protocol data indicates not only that certain aspects of the teaching outline provided powerful tools for transforming some of the pre-algebraic concepts, but also that contradictory notions seemed to coexist in the learner's conceptual framework and that some of these proved to be quite resilient to instruction.