The spontaneous speech of a Mohawk-speaking boy was recorded from age 2;10 to 4;1. Analysis of this speech indicated that certain verbal prefixes are acquired earlier than suffixes. The pronominal prefix of nouns, on the other hand, enters late. Yet, before the appearance of any nominal affix, the child already uses a pronominal possessive as a free form. Its status is that of a noun. The pattern of verb-affix acquisition appears to be language particular. The pattern of affix acquisition in general conforms to the well-known principle that irregular forms are mastered later than regular ones. Data also stress the importance of low frequency forms. These might mark important transitional periods within a child's speech development. Language acquisition research that focuses mainly on quantitative material might thus ignore important strategical clues. Overgeneralization in a child's speech is not only indicative of capacity to differentiate, but it may also reveal the manner in which new linguistic information is processed. (Author/JB)