This paper describes the construction of a 26-item "Manic-State Rating Scale" (MS Scale) for use with hospitalized patients. Interrater reliability among the members of the nursing team was high for all items. Comparison of the scale item scores with independent global mania ratings by psychiatrists and an independent manic symptom checklist by nurses yielded high correlations for 22 of the items. This suggests that the scale provides a valid method for measuring manic symptomatology. Six of the scale items were found to be particularly useful in measuring changes in the severity of mania as reflected in the total MS Scale score. It is suggested that the further evaluation of manic and hypomanic patients using the MS Scale may yield items which will help to define individual differences among manic patients.