Purpose: We compared copula and auxiliary verb BE use by African American English-speaking children with and without a creole heritage, using Gullah/Geechee as the creole criterion, to determine if differences exist, the nature of the differences, and the impact of the differences on interpretations of ability. Method: Data came from 38 children, aged 5 to 6 years (19 with Gullah/Geechee and 19 without Gullah/Geechee heritage). All were developing language typically, with groups matched on gender, maternal education, and, when possible, test scores. The children's productions of BE were elicited using a screener, probes, and language samples. Results: Although many similarities were documented, the 2 groups' BE systems differed in 3 ways: use of unique forms (i.e., "d?"), unique use of shared forms (i.e., BEEN), and rates of use of shared forms (e.g., "am," "is," "was"/"were," "was" for "were"). Although most noticeable in the language samples, differences surfaced across tasks and showed the potential to affect interpretations of ability. Conclusions: Dialect variation that is tied to children's creole heritage exists, involves 3 types of variation, and potentially affects interpretations of ability. Effects of a heritage language and different types of variation should be considered in research and clinical endeavors with African American English-speaking children.