Characteristics of instruments developed by nurses for use in evaluating delirium/acute confusional states include relative emphasis on observable behavior and the need to impose low respondent burden. Two instruments that have been most used by nurse researchers are described: The Confusion Rating Scale and the NEECHAM Confusion Scale. The former is based on observable behavior; the latter incorporates vital function and oxygen saturation measurements that may serve as early warning sings of impending delirium.