Purpose: To investigate children's performance on a fast mapping task. Possible effects across age, dialect group, and clinical status were explored. Method: Participants between the ages of 4 and 9 saw a series of pictured events and heard novel verbs. The novel verbs were in intransitive, transitive, dative, and complement syntactic frames or argument structures. The children then had to answer questions about the novel verbs that revealed what meaning they had attached to them. The field-testing of a new assessment instrument provided the data for typically developing children and children with language impairment from 2 linguistic communities: (a) mainstream American English speaking and (b) African American English speaking. Strict criteria were used for the 529 participants that defined both their clinical and dialect status. Results: There were significant effects of age and clinical status on the participants' ability to fast map a novel verb from its argument structure, but no significant effects for dialect. Conclusions: Regardless of dialect, children with specific language impairment have difficulty using syntactic frames to identify a likely meaning of a novel verb. In addition, the syntactic frames are differentially difficult, with complement structures being particularly hard.