Objectives-The development and validation of the Center for Neurologic StudyLability Scale (CNS-LS), the first self report measure of aVective lability in patients with amyotrophic lateral sclerosis (ALS). Methods-Potential questionnaire items were identified through interviews with patients and families and expert review. Potential items, as well as measures of aVect intensity, aVective lability in psychopathology, and depression were administered to 99 patients with ALS for item selection and the examination of factor structure and construct validity. Testretest reliability was examined using an additional sample of 31 patients with ALS, and criterion related validity was examined by comparing CNS-LS scores with physicians' diagnoses of aVective lability in a sample of 77 patients with ALS. Results-A seven item questionnaire emerged, composed of two subscales measuring labile laughter (four items) and labile tearfulness (three items). The CNS-LS showed a pattern of associations with aVect intensity, aVective lability in psychopathology, and depression consistent with a scale measuring aVective lability. The CNS-LS also showed good testretest reliability and internal consistency, and successfully predicted physicians' diagnoses of aVective lability. An auxiliary subscale measuring labile frustration, anger, and impatience also emerged. Conclusions-The CNS-LS is a short, easily administered, and psychometrically sound measure of aVective lability for use with patients with ALS. It has potential applications as both a clinical screening device and a research tool. The need for future research into the relation of depression as well as labile frustration, anger, and impatience to the syndrome of aVective lability in neurological disorders is discussed.

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