The phenomenon of `lucid dreaming' is discussed in this article. Characteristic for lucid dreams is that the dreamer is `awake' to the inner world of his dream, while being asleep in regard to the physical environment. The principal concept of `reflectivity' in the dream-theory of Rechtschaffen is discussed first. Then the mental functions that reintegrate in the lucid dream are pointed out. The lucid dream is distinguished from other (altered) states of consciousness. The psychoanalytic views on lucid dreaming are briefly mentioned. Finally the therapeutic implications are indicated.