Six patients with persistent trigeminal artery (PTA) and one patient with its variant (PTAV) were studied using a 1.0-T magnetic resonance unit. With both magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), four of the six PTAs were detected as abnormal connecting arteries between the cavernous internal carotids and the basilar arteries. The remaining two PTAs and one PTAV were not detected using MRI, but were imaged by MRA. It was concluded that relatively large PTAs can be detected using MRI, but small PTAs and PTAVs may be missed using MRI.