Pressure vertigo or alternobaric vertigo is the type of vertigo normally associated with relative overpressure in the middle ear. As with other types of vertigo, it should occur only if there is unequal stimulation of the left and right vestibular systems: there should be a lawful relation between the orientation of the head, the side of the overpressured ear, and the direction of apparent movement. Few published accounts give information on all these aspects. This paper reports some old and new cases which suggests that, when the head is upright during the ascent, overpressure in the right ear causes apparent bodily and visual movement to the right (clockwise), while overpressure in the left ear has the opposite effect. Horizontal orientation of the head probably reduces the vertigo. There are no detailed and unequivocal reports of pressure vertigo during descent, or with the head inverted. Some reports exist of tumbling sensations and of tilting of the visual scene, but the exact circumstances are unclear.