Because no rigorously validated, simple yet accurate continuous delirium assessment instrument exists, we developed the Nursing Delirium Screening Scale (Nu-DESC). The Nu-DESC is an observational five-item scale that can be completed quickly. To test the validity of the Nu-DESC, 146 consecutive hospitalized patients from a prospective cohort study were continuously assessed for delirium symptoms by bedside nurses using the Nu-DESC. Psychometric properties of Nu-DESC screening were established using 59 blinded Confusion Assessment Method (CAM) ratings made by research nurses and psychiatrists. DSM-IV criteria and the Memorial Delirium Assessment Scale (MDAS) were rated along with CAM assessments. Analysis of these data showed that the Nu-DESC is psychometrically valid and has a sensitivity and specificity of 85.7% and 86.8%, respectively. These values are comparable to those of the MDAS, a longer instrument. Nu-DESC and DSM-IV sensitivities were similar. The Nu-DESC appears to be well-suited for widespread clinical use in busy oncology inpatient settings and shows promise as a research instrument.