The Southern California Postrotary Nystagmus Test (SCPNT) provides an objective assessment of nystagmus. Although depressed nystagmus duration as measured by the SCPNT is considered a major sign of vestibular dysfunction in learning-disabled children, the reliability of the SCPNT with this population has not been established. To study reliability of nystagmus duration in this population, 89 learning-disabled children were evaluated with the SCPNT. The results demonstrated that this sample had significantly depressed scores and more variability in scores than normal children. Intrascorer and test-retest reliabilities, although statistically significant, were lower than those established with normal children. A test-retest study of the reliability of placing a child in a deviant duration range over time significantly reduced reliability estimates. Clinicians using nystagmus duration scores in the evaluation of vestibular dysfunction in learning-disabled children should be sensitive to the variation in this measure in this population.