Opsoclonus is a rare but distinctive disorder of ocular motility. Although there are many reported cases of opsoclonus in children, there is no large series of cases in adults. In recent years, three cases of opsoclonus in adults have been identified at the University of Iowa, Iowa City. Review of 55 other cases of opsoclonus in adults reported in the literature showed that adults over 40 years of age with onset of opsoclonus should be investigated fully for underlying malignancy. In younger adults with a history of a preceding influenzalike illness, viral titers (acute and convalescent) should be obtained. Also, younger adults should be investigated for other causes of opsoclonus, such as drug or toxin exposure. Treatment is directed toward correcting the underlying process.