Teachers need to expand their understanding of language in order to meet the diverse language and literacy needs of their students. Students may demonstrate deficits in the domains of language form (phonology, morphology, syntax), content (semantics), and use (pragmatics). However, existing studies have only investigated teachers' knowledge of language form. Therefore, this study investigated 236 preservice and inservice teachers' knowledge of language form, content, and use as well as the teacher characteristics that may influence this knowledge. Both preservice and inservice teachers were found to have low levels of language knowledge. Experienced teachers, inservice teachers, and inservice teachers taking graduate level courses at a university tended to perform better than preservice teachers with no teaching experience on all three subscales. These findings have implications for teacher training programs and for professionals providing support services to classroom teachers. (Contains 3 tables and 1 figure.)