Background: Basilar artery hypoplasia (BAH) was considered if the outer diameter in the upper 1.0 cm segment was less than the common range (3.0 mm~ 5.5 mm). The patients I encountered at a regional hospital in Tao-Yuan were reviewed. Methods: Between 2008 and 2010, 96 patients with magnetic resonance imaging with a time-of-flight angiogram scheduled by the author were reviewed. Results: Twelve patients (3 male and 9 female) with BAH were enrolled. The average age was 49.8 years (S.D.=11.9). Of them, 58.3% (n=7) were diagnosed with vertebrobasilar artery insufficiency; besides, 83.3% (n=10) had vertebral artery hypoplasia, and 66.7% (n=8) had fetal type posterior cerebral arteries, but none had a persistent trigeminal artery. All of them were treated conservatively. Finally, the symptoms of 58.3% (n=7) were well controlled, and that of the others were cured. Conclusions: The prevalence of BAH was 12.5% on magnetic resonance imaging with time-of-flight angiograms of those that had been bothered by dizziness, headache or tinnitus for at least three months, and were suspected of a central lesion. Conservative treatment was recommended.