Complex Instruction is a multifaceted instructional model designed to provide highly challenging learning opportunities for students in heterogeneous classrooms. The model provides a rationale for and philosophy of creating equity of access to excellent curriculum and instruction for a broad range of learners, guidance for preparing students for successful groupwork, direction for the teacher's role, and principles and practices for "groupworthy tasks"--assignments worthy of student investment and designed to draw on a broad range of abilities for successful task completion. This article focuses on the nature and importance of "groupworthy tasks."