In the United States, new common state standards in English language arts and disciplinary literacy require K-12 students to "read and comprehend complex literary and informational texts independently and proficiently." Issues of text complexity have spurred debates in the mainstream literacy, educational practice, and policy communities. Issues raised for English learners (ELs)--and their teachers--are even more vexing. This article considers first language (L1) and second language (L2) reading theory and research to articulate challenges facing ELs as they engage with complex text and to evaluate instructional responses. Reviewing historical and contemporary perspectives on text complexity and reading comprehension, the authors argue that (a) the complexity involved in comprehending difficult text transcends textual features to include dimensions of the reader, task, and pedagogical support; and (b) the path to success for ELs will not be paved solely by attempting to match readers with "appropriate" texts or by modifying existing texts to meet perceived student reading levels. If what is "complex" about reading certain kinds of texts is the relationship among the text, its reader, the task the reader is being asked to perform, and the context in its multiple dimensions, then pedagogical responses for ELs must keep all of these in mind.