Computer processing made it feasible for us to base our study of the vocabulary of six-year-old Navajo children on as large a corpus as we could collect in the time available. Our difficulties, as so often in computational linguistics, were with matters of linguistic theory rather than of computing. What we ran into was the as-yet unsolved question of the nature of the word in Navajo: how many affixes should be written as part of the verb and how many as separate words; and how does one handle the unbelievably complex morphophonemics in choosing headwords. The computer once again showed its ability, not just as an aid in handling large bodies of data, but as a heuristic device that makes clear to the researcher the limitations of his understanding of the material he is working with.