BACKGROUND: Among several types of ischemic stroke (IS), branch atheromatous disease (BAD) is known to be the leading cause of disability. METHODS: A total of 1919 patients with acute IS were retrospectively analyzed, and BAD patients were classified into anterior or posterior BAD, depending on the responsible vascular territories. These patients were further subcategorized with or without early neurologic deterioration (END or no-END). RESULTS: Of all IS patients, 14.3% had BAD, and 202 patients (73.7%) were further classified as anterior BAD and 72 patients (26.3%) as posterior BAD. The prevalence of diabetes mellitus and END was significantly higher in posterior than in anterior BAD (44.4% vs 26.4%, P < .01; 18.1% vs 5.4%, P < .01, respectively). Posterior BAD showed a higher proportion of female patients and an older age (69.2% vs 39.0%, P < .05; 79.1 ± 7.7 vs 70.5 ± 10.7, P < .01, respectively) in END than in no-END. The modified Rankin Scale was worse in posterior BAD at 90 days (2.5 ± 1.6, P < .01) than in anterior BAD (1.6 ± 1.4). CONCLUSIONS: Our present study shows that posterior BAD is a worse clinical outcome than anterior BAD, with more vascular risk factors. Older female patients with posterior BAD showed a higher risk of END, leading to a worse clinical outcome.