Everyday intuitions suggest full conscious control of behavior, but evidence of unconscious causation and automaticity has sustained the contrary view that conscious thought has little or no impact on behavior. We review studies with random assignment to experimental manipulations of conscious thought and behavioral dependent measures. Topics include mental practice and simulation, anticipation, planning, reflection and rehearsal, reasoning, counterproductive effects, perspective taking, self-affirmation, framing, communication, and overriding automatic responses. The evidence for conscious causation of behavior is profound, extensive, adaptive, multifaceted, and empirically strong. However, conscious causation is often indirect and delayed, and it depends on interplay with unconscious processes. Consciousness seems especially useful for enabling behavior to be shaped by nonpresent factors and by social and cultural information, as well as for dealing with multiple competing options or impulses. It is plausible that almost every human behavior comes from a mixture of conscious and unconscious processing.