Interviews with 108 Navajo children from bilingual first grade classes on Navajo reservations were recorded. Analysis of the interviews focused on phonological, grammatical, and lexical features that show a systematic variation within the speech of individuals or between individuals. Variable features were compared with background factors such as age, sex, geographical provenance, clan membership, and previous educational experience, in order to determine any correlations or effects. In addition, samples of the children's utterances were submitted to a panel of adult Navajo speakers to obtain their judgments on appropriateness and grammaticality of the forms used. Finally, interview data were analyzed to discover possible effects of English bilingualism on the students' competence and proficiency in Navajo. Analysis was also carried out on the English data to determine interference and order of acquisition of selected features. (Author/JB)