This retrospective pilot study was conducted to examine the validity of upper extremity Motricity Index scores. The strength of the paretic upper extremity of 10 patients with stroke was measured using the Motricity Index and dynamometry. Specifically measured were hand-grasp, elbow flexion, and shoulder abduction. The criterion validity of the Motricity Index scores was supported by their significant and high correlations with dynamometer measures (r >.74). The construct validity of the Motricity Index scores was demonstrated by their high Cronbachís alpha (.968). The Motricity Index is a valid instrument for characterizing the strength of the paretic upper extremity following stroke.