Add to ORKGKey words: complementarity; mind-body problem; quantum entanglement; consciousness Neuroendocrinology Letters 2000; 21:221–232 Copyright © Neuroendocrinology Letters 2000 Abstract We describe the concept of complementarity and argue that it is a useful concept for consciousness and other studies at the interface of conscious phenomena and physical reality. After outlining the history and source of the concept within psychology, we describe its place as a working hy-pothesis for the mind-brain problem. We then point out that generalized quantum non-locality could be of importance even for macroscopic ob-jects. If this is so, complementarity would be the key-concept to under-stand EPR-like correlated systems. P