Horizontal eye displacement in total darkness during lateral tilting about the body axis was examined in 14 patients with unilateral loss of labyrinth function, including 8 cases of positional vertigo or dizziness and 6 symptom-free cases. The change in eye displacement following labyrinthectomy was also studied in 2 cases of labyrinthitis and one case of delayed hydrops. Seven out of 8 subjects suffering from positional vertigo or dizziness exhibited abnormal eye displacement on tilting to the affected side, while 5 out of 6 symptom-free subjects showed normal eye displacement. The correlation between anomalous eye displacement and the presence of subjective symptoms was statistically significant (p less than 0.05). Abnormal eye displacement following labyrinthectomy was readily noted within 2 weeks of surgery, but became almost undetectable 3 to 4 weeks postoperatively, in close accordance with a decrease in positional vertigo or dizziness. It was concluded that the measurement of eye displacement during lateral body tilt, although previously reported to be useful in the assessment of function, might also be employed to examine compensation for the loss of otolith function.