OBJECTIVE AND IMPORTANCE: An infraoptic course of the proximal anterior cerebral artery is a rare anomaly that has been reported in 32 cases to date, often in association with cerebral aneurysms. This anomaly represents a maldevelopment in the embryogenesis of the anterior circle of Willis, resulting from the persistence of the primitive prechiasmal arterial anastomosis or an error in the development of the definitive ophthalmic artery (OphA). The case of a patient with a ruptured middle cerebral artery aneurysm and an anterior communicating artery aneurysm associated with this anomaly is described, and the anatomic features are outlined. CLINICAL PRESENTATION: A 30-year-old male patient with a right temporal hematoma and subarachnoid hemorrhage was admitted to our department 4 days after the hemorrhaging episode, with normal neurological examination results. Angiography revealed a right middle cerebral artery aneurysm and an anterior communicating artery aneurysm with an anomalous precommunicating tract. INTERVENTION: The patient was surgically treated 14 days after the hemorrhaging episode, through a right frontopterional craniotomy; both aneurysms were excluded by clipping. The anomalous infraoptic proximal tract of the anterior cerebral artery was well documented, with its origin adjacent to the OphA. The patient remained neurologically intact after surgery and was discharged 8 days later. CONCLUSION: The anomalous infraoptic course of the proximal anterior cerebral artery was associated with a low bifurcation of the ipsilateral internal carotid artery and the absence of the contralateral precommunicating tract in this patient. The strict anatomic relationship with the origin of the OphA suggests an error in the development of the definitive OphA, with persistence of an anastomotic loop between the primitive dorsal and ventral OphAs. It is concluded that, for aneurysm surgery, careful angiographic evaluation and an understanding of the neurovascular relationships in the circle of Willis are essential for a successful postoperative course, especially when very rare vascular anomalies are treated.