Purpose: To examine 3 forms ("am," "is," "are") of auxiliary BE production by African American English (AAE)-speaking children with and without specific language impairment (SLI). Method: Thirty AAE speakers participated: 10 six-year-olds with SLI, 10 age-matched controls, and 10 language-matched controls. BE production was examined through samples and a probe. Results: Across tasks, visual inspection suggested that the children with SLI overtly marked BE at lower rates than the controls, and all groups marked "am" at higher rates than "is" and "are," with few dialect-inappropriate errors. Within the samples, the children also overtly marked "is" at higher rates when preceded by "it"/"that"/"what" than when it was preceded by a personal pronoun. A subset of these results was confirmed statistically. The children's marking of BE also varied across tasks; for the age-matched controls, this variation was tied to their AAE dialect densities. Conclusions: These findings show across-dialect similarities and differences between children's acquisition of AAE and mainstream American English. Similarities involve the rate of the children's BE marking as a function of their clinical status and the nature of their dialect-inappropriate errors. Differences involve the children's rates of BE marking as a function of the form, context, and task.