Previous case reports of vertebral-basilar system infarction following chiropractic cervical manipulation have emphasized the role of predisposing factors such as cervical spondylosis, atherosclerosis, and congenital asymmetry of the posterior circulation. Ten patients without prior neurologic symptoms had vertebral-basilar system infarction promptly after chiropractic maneuvers. One patient, who was free of clinical and radiographic evidence of predisposing factors, subsequently died. Autopsy studies revealed massive nonhemorrhagic brainstem infarction due to bilateral vertebral artery thrombosis. Nine patients survived with residual neurologic deficits due to lesions in various locations of the posterior circulation. No patient received anticoagulants. Previous case reports are summarized and the kinetic anatomy of the vertebral arteries is reviewed to clarify the potential mechanisms involved in the pathogenesis of this entity. Although a causal relationship may be difficult to establish in individual cases, cervical manipulation seems to be the major identifiable factor in the pathogenesis of stroke in some patients.