BACKGROUND AND PURPOSE: Progression of motor deficits in the acute period is frequently observed in patients with subcortical striatocapsular infarctions. Therefore, we sought to determine the factors associated with early motor progression in patients with infarcts confined to the striatocapsular region. METHODS: We studied 80 consecutive patients with striatocapsular-region infarction, as defined by clinical and MRI criteria, within 24 hours after stroke onset. Motor progression was defined as an increase of >2 points in the motor items of the National Institutes of Health Stroke Scale (NIHSS) within 7 days of stroke onset. The study population was divided into patients with and without motor progression, and risk factors, clinical features, and brain MRI/magnetic resonance angiograpy (MRA) findings were compared between these groups. RESULTS: Motor progression was observed in 40% of the 80 patients. The independent variables associated with motor progression were a history of hypertension (OR=7.8, 95% CI=1.5-39.8, p=0.013) and an initial infarct extent of > or =15 mm (OR=9.2, 95% CI=1.8-45.7, p=0.006). However, there were no differences in the initial NIHSS score, other stroke risk factors, vascular stenosis pattern, or cardioembolic source. CONCLUSIONS: Early motor progression in patients with striatocapsular-region infarction is associated with the initial extent of the lesion. However, the stroke mechanism and vascular stenosis did not differ between the motor progression and stable groups.