PURPOSE: To study the association between petrous carotid canal (PCC) and internal carotid artery (ICA) stenoses in patients with malignant osteopetrosis. MATERIALS AND METHODS: Mean and minimum PCC diameters obtained from cranial computed tomographic (CT) scans in 20 patients were compared with similar measurements in 52 control subjects. ICA caliber, evaluated with magnetic resonance (MR) arteriography, was correlated with age and PCC dimensions. RESULTS: There was a statistically significant difference between patient and control PCC diameters. There was a strong positive correlation between age and PCC diameter in the control subjects, but only a weakly positive correlation in the patients. One or both ICAs were stenotic on all patient MR arteriograms. MR angiographic stenosis grade correlated positively with age but not with PCC diameters. CONCLUSION: PCC and ICA stenoses occur frequently in patients with malignant osteopetrosis. Bony overgrowth or a 'persistent fetal state' may produce the PCC stenoses. The findings do not support progressive PCC narrowing in these patients.