Much has been said lately about hypnotic dreams. I commented recently on opinions of Barber, Tart, Moss, and Hilgatd (1969). Elsewhere I said that hypnotic dreams are often indistinguishable in structure from spontaneous nocturnal dreams, but functional differences may involve a variety of neuropsychological and psychophysiological correlates. Remarkably little has been said about hypnotic nightmares. I mentioned that some patients may try successfully or unsuccessfully to extricate themselves from such nightmares (1966). If successful they may remain in hypnosis or emerge from it spontaneously. If unsuccessful, the hypnotic nightmare simply runs its course as does any dream. The hypnotherapist may intervene if necessary to terminate the hypnotic nightmare or the hypnotic session. Patients with such nightmares tend to have strong emotional reactions in their interpersonal relations. Hysterical components may be evident. Patients' hypnotic nightmares like ordinary hypnotic dreams may resemble patients' spontaneous nocturnal imagery (1965, 1966). An example of a hypnotic nightmare is offered to highlight such occurrences and focus attention on the interest they deserve. A middle-aged compulsive patient described in hypnoanalysis a couple of hypnotic dreams and was told he would have another which he would be able to interpret. He was silent awhile but eventually began to moan and to breathe deeply and rapidly until finally he relaxed. He said he dreamed he saw water spurting upward as from a fountain. Then the spray separated into two parts. Afterwards the spurting water changed into an erupting volcano, spewing rocks and flaming lava while people around it fled in terror in all directions. He became very frightened. The dream ended. Still in hypnosis he associated to the spurting water as seminal ejaculation which reminded him of masturbating as a child and being fearful of parental discovery and punishment and of his efforts to hide evidence of his activity. The separation of the spray suggested the separating labia of female genitals. He saw the volcanic eruption as explosion of his own hostility and aggression, the consequences of which he feared. Fright now was reflected in his physical reactions and the view of the dream people rushing about frantically trying to escape. This reminded him of the last days of Pompeii which he believed had been related to sexual excesses and abetrations that incurred the wrath and punishment of the gods. While the sexual themes played a role in this patient's compulsions, his actual sexual functioning during intercourse presented no problems. The repressed and suppressed aggressions, however, were quite troublesome. The differences in impulse control are reflected in the dream imagery, its nightmarish features, and the patient's psychophysiological responses. The neuropsychological (such as imagery-electrocottical activity) and psychophysiological (such as imagery-cardiovascular activity) correlates of the hypnotic nightmare deserve further investigation in clinical and experimental settings.