The first documented case of cerebrovascular disease occurring in a 13-year-old girl with purine nucleoside phosphorylase deficiency is reported. This patient, the oldest known survivor with purine nucleoside phosphorylase deficiency, had previously experienced multiple sequential neurologic problems. She presented with episodes of transient left hemiparesis, followed shortly thereafter by dense left hemiplegia. Magnetic resonance imaging revealed a right internal capsule infarct; cerebral angiography revealed vasculopathy of the proximal vessels. Proposed mechanisms for neurologic dysfunction and cerebrovascular disease in purine nucleoside phosphorylase deficiency are discussed.