The study examined children's use of verbal -s marking (e.g., he "walks") in two nonmainstream dialects of English, African American English (AAE), and Southern White English (SWE). Verbal -s marking was of interest because there are gaps in the literature about the nature of this structure within and across typically developing children who speak AAE and SWE and about the nature of this structure in AAE- and SWE-speaking children with specific language impairment (SLI).To address these gaps, children's verbal -s marking was examined as a function of their dialect and clinical status and as a function of a number of linguistic variables. These included: verb regularity, negation of the utterance, meaning of the verb phrase (+/- habitual and/or historical present and +/-historical present), and type of subject preceding the verbal -s form. Data came from 57 language samples elicited from six-year-olds (26 were speakers of AAE and 31 were speakers of SWE; 26 with SLI and 31 without SLI).The results indicated that the children's verbal -s marking varied as a function of their dialect. For the SWE-, but not the AAE-speaking groups, the children's marking also varied by their clinical status. In addition, the results indicated that four of the linguistic variables influenced the children's marking of verbal -s in different ways. Negation of the verb phrase affected the verbal -s marking of three of the four groups, and the direction of the influence was consistent with the adult literature; habituation of the verb phrase also affected the verbal -s marking of all four groups, but the direction of the influence ran counter to what has been documented in the adult literature; and verb regularity and historical present tense affected the verbal -s marking of the SWE-, but not AAE-speaking groups. For type of subject, the data were insufficient to evaluate the effect of this variable on the children's rates of marking. Finally, the results showed that all four speaker groups produced six different types of nonmainstream verbal -s forms, and they also produced a range of different verb types with the verbal -s structure. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]