Purpose: This study examined African American English--speaking children's use of BE, DO, and modal auxiliaries. Method: The data were based on language samples obtained from 48 three-year-olds. Analyses examined rates of marking by auxiliary type, auxiliary surface form, succeeding element, and syntactic construction and by a number of child variables. Results: The children produced 3 different types of marking (mainstream overt, nonmainstream overt, zero) for auxiliaries, and the distribution of these markings varied by auxiliary type. The children's nonmainstream dialect densities were related to their marking of BE and DO but not modals. Marking of BE was influenced by its surface form and the succeeding verbal element, and marking of BE and DO was influenced by syntactic construction. Conclusions: Results extend previous studies by showing dialect-specific effects for children's use of auxiliaries and by showing these effects to vary by auxiliary type and children's nonmainstream dialect densities. Some aspects of the children's auxiliary systems (i.e., pattern of marking across auxiliaries and effects of syntactic construction) were also consistent with what has been documented for children who speak other dialects of English. These findings show dialect-specific and dialect-universal aspects of African American English to be present early in children's acquisition of auxiliaries.