In this centenary of Freud's The Interpretation of Dreams, it is important to revisit this classic, to discuss why it is a classic, to consider what has been learned since its publication, and to discuss what changes in our understanding of dreams and dreaming are called for. To this end, we briefly discuss some of the main themes of the book. Then we review both changes in psychoanalytic thinking and theory and the results of many studies made possible by the discovery of the electroencephalographic changes that occur during sleep and their relevance for understanding dreams and their function. We suspect that Freud would have been delighted to know about this explosion of information about the physiology of dreaming. With this in mind, we consider the need for modification of some of Freud's theories while noting that his basic contribution, that dreams are meaningful and understandable, has been amply confirmed. We then discuss these observations in relation to how we approach working with dreams.