Arteries from the first segment of the middle cerebral and adjacent normal blood vessel specimens were collected from 19 patients who had died from cerebral infarction. According to morphologic examination the atherosclerotic plaque present was classified as stable or unstable. The expression of ubiquitin conjugates and nuclear factor kappa B (NF-κB) was assessed and found significantly higher in plaques than normal tissue and higher in unstable plaques than in stable plaques. Ubiquitin conjugates and NF-κB were positively correlated with each other. It was concluded that the ubiquitin proteasome system and NF-κB possibly play a role in the development of atherosclerotic plaques in intracranial arteries. J. Cell. Physiol. 227: 784–788, 2012. © 2011 Wiley Periodicals, Inc.