Assessment can provide information about student learning and the effectiveness of classroom strategies, but what are the special considerations when used with English learners? To better understand the research about how schools and systems can support multilingual learners through assessment, Elizabeth Foster spoke with Margo Gottlieb, an expert in curriculum, instruction, and assessment of language learners and author of more than 90 articles, monographs, handbooks, guides, technical reports, chapters, and assessments. This article summarizes the conversation with Gottlieb, sharing a range of insights about the critical nature of assessment as it relates to understanding multilingual learners. Like other experts highlighted in this issue of "The Learning Professional," Gottlieb stresses the importance of recognizing the strengths multilingual students bring to the classroom. As she says, "If you only look through a monolingual lens, you don't know the whole child."