This report describes a new stressful procedure and the constellation of symptoms manifested by persons subjected to this stress. The procedure consists essentially of carrying out activities in a slowly rotating room. The symptoms most nearly resemble those observed in motion sickness,4,15,22but certain similarities are also seen when comparison is made with the symptomatology in vasodepressor states,5,21in anxiety and depressive states, in sleep, and, indeed, in various disturbances characterized by psychosomatic symptoms.20Inasmuch as the symptoms are the direct or indirect result of stimulation of the semicircular canals, the most precise term covering the general symptomatology is probably "canal sickness."8Although the procedure is specifically applicable to studies of the function of the semicircular canals, it has additional usefulness as a means of investigating certain aspects of the brain stem-activating system.3,6,10,11,14,17The extraordinary flexibility of the procedure in terms of both the strength