Background: The National Institutes of Health Stroke Scale (NIHSS) can objectively quantify the severity of stroke. However no information is available about psychometric properties and it’s applicability in the Iranian population.

Objectives: The present study purposed by utilization of this instrument for neurological deficits measurement due to stroke, to determine the internal consistency reliability and concurrent validity of NIHSS to separate two groups of men and women patients.

Materials and Methods: In a cross-sectional study, 206 ischemic stroke patients were selected and the internal consistency reliability and concurrent validity of NIHSS were assessed. For this purpose, Barthel index that measures the functional disability was used. Data also were analyzed by Independent t-test, Chi-square, Pearson correlation, Fisher's z tests and bivariate regression analysis.

Results: Internal consistency for men (α=0.881), women (α=0.913) and total patients (α=0.893) was excellent. Negative correlation was found between NIHSS and Barthel index in both men (r=-0.43, p<0.0001) and women (r=-0.63, p<0.0001) and this relationship estimated to be more significant among women rather than men (p<0.05). In addition, NIHSS scores could significantly predict the Barthel score in both groups (p<0.0001) but the results revealed the more ability of NIHSS in predicting functional disability for women (R²=0.40) rather than men (R²=0.18).

Conclusion: Persian version of NIHSS was reliable and valid instrument that can be applicable in both men and women with ischemic stroke; however, it was found that the degree of concurrent validity is better among women than men.