Study objective: The Cincinnati Prehospital Stroke Scale (CPSS) is a 3-item scale based on a simplification of the National Institutes of Health (NIH) Stroke Scale. When performed by a physician, it has a high sensitivity and specificity in identifying patients with stroke who are candidates for thrombolysis. The objective of this study was to validate and verify the reproducibility of the CPSS when used by prehospital providers. Methods: The CPSS was performed and scored by a physician certified in the use of the NIH Stroke Scale (gold standard). Simultaneously, a group of 4 paramedics and EMTs scored the same patient. Results: A total of 860 scales were completed on a convenience sample of 171 patients from the emergency department and neurology inpatient service. Of these patients, 49 had a diagnosis of stroke or transient ischemic attack. High reproducibility was observed among prehospital providers for total score (intraclass correlation coefficient [r_I], .89; 95% confidence interval [CI], .87 to .92) and for each scale item: arm weakness, speech, and facial droop (.91, .84, and .75, respectively). There was excellent intraclass correlation between the physician and the prehospital providers for total score (r_I, .92; 95% CI, .89 to .93) and for the specific items of the scale (.91, .87, and .78, respectively). Observation by the physician of an abnormality in any 1 of the 3 stroke scale items had a sensitivity of 66% and specificity of 87% in identifying a stroke patient. The sensitivity was 88% for identification of patients with anterior circulation strokes. Conclusion: The CPSS has excellent reproducibility among prehospital personnel and physicians. It has good validity in identifying patients with stroke who are candidates for thrombolytic therapy, especially those with anterior circulation stroke. [Kothari RU, Pancioli A, Liu T, Brott T, Broderick J: Cincinnati Prehospital Stroke Scale: Reproducibility and validity. Ann Emerg Med April 1999;33:373-378.]