A prolonged hypnosis was developed in guinea pigs, from a few seconds to a few minutes'' duration in adults. In training, when the animal rights itself it is immediately returned to the dorsal position. The procedure is continued for 2 hrs. daily. The state could be broken by means of visual, auditory, or tactile stimuli. The guinea pig usually shows exophthalmus, eyeballs deviated downward and forward, paws extended, and often a fine tremor. The acquired aptitude for prolonged hypnotic state may be fixed for a long time. Guinea pigs differ in responses. Animals with a long initial spontaneous hypnotic state exhibit the longest reaction after training. Some animals are easier to train in a lateral than in a dorsal position. Animals which are put on one side only during training exhibit prolonged reactions only or especially on that side. Generally the eye signs are unilateral in such animals. A prominent sign of successful training is the relative ineffectiveness of intrusive stimulation. There is a functional gradation in the intensity of stimulation needed to discontinue a prolonged state of hypnosis. Thus another guinea pig in the visual field is more effective than an artificial visual stimulus. In an animal trained in a lateral hypnogenic position, stimuli may be more effective on one side.