Polysynthetic languages can present special extraction puzzles to children, due to the length of their words. A number of hypotheses concerning children's strategies for acquiring morphology, originally proposed on the basis of their approaches to somewhat simpler systems, are confirmed by observations of five children acquiring Mohawk. Among the Mohawk children, the earliest segmentation of words was phonological rather than morphological: stressed syllables, usually penultimate or antepenultimate, were extracted first. Ultimate syllables were then added, confirming the salience of the ends of words. During this time, distinctions expressed by adults in affixes were either omitted or expressed analytically. Acquisition then moved leftward by syllables. When most utterances were long enough to include pronominal prefixes as well as roots, morphological structure was apparently discovered. It is not surprising that the pronouns should trigger this awareness, since they are frequent, appearing with every verb and most nouns, they are functional, and they are semantically transparent. From this point on, the children acquired affixes primarily according to their utility and semantic transparency rather than their phonological shape or position.