The present study investigated the role of vocabulary depth in reading comprehension among a diverse sample of monolingual and bilingual children in grades 2-4. Vocabulary depth was defined as including morphological awareness, awareness of semantic relations, and syntactic awareness. Two hundred ninety-four children from 3 schools in a Mid-Atlantic district and 3 schools in a Northeastern school district participated in the study and were assessed at the beginning and end of one school year on a wide variety of language and literacy measures. Bilingual children were assessed in English and Spanish. A latent difference score model that assessed change in a latent indicator of English reading comprehension from Time 1 (Fall) to Time 2 (Spring) was tested with results showing that vocabulary depth measures made significant contributions to initial status, but not change, in reading comprehension over and above between-subjects factors (grade, ethnicity, language status) and baseline control within-subject factors (word identification and vocabulary breadth). There was no added contribution of Spanish language measures to English reading comprehension among the bilingual students.