The authors studied two groups of young men: short sleepers who habitually slept less than six hours and long sleepers who slept more than nine hours a night. The short sleepers as a group tended to be action-oriented, mildly compulsive people with hypomanic trends, who characteristically used mechanisms of denial, avoidance, and 'keeping busy' to bind anxiety. The long sleepers tended to be introspective, mildly depressed, and anxious people with neurasthenic trends. Most striking in the findings was that the two groups had identical periods of nondream (Stages 3 and 4) sleep, and that the difference appeared to be that long sleepers required a good deal more dream time. The suggestion is that the character structures that failed to bind anxiety in the long sleepers required a greater period of dreaming for dynamic function in maintaining psychic equilibrium. Various character structures may therefore typically require differing amounts of dream time, depending upon the effectiveness with which their defenses bind anxiety.