The term "atheromatous pseudoocclusion" of the internal carotid artery (ICA) describes an extreme type of stenosing lesion which, during non-invasive procedure and conventional angiography is easily misdiagnosed as complete occlusion. Its recognition requires special sonographic and angiographic techniques. Nine subjects with pseudoocclusion could be observed during the last 12 months, most of them presenting minor strokes. Infarction suggesting a haemodynamic pathogenesis were demonstrated in seven of the cases by computed tomography. In seven of the eight subjects that were operated on, ICA reconstruction was successful. Since pseudoocclusion of the ICA is likely to progress rapidly to definite occlusion, the patient is severely jeopardized from periocclusive embolism into the major brain arteries. Immediate diagnostic clarification and emergency endarterectomy are mandatory.