The vessels that supply the basal ganglia and thalami are not normally conspicuous on the cranial sonograms of neonates. Twelve neonates with abnormally echogenic or "bright" vessels on cranial sonograms were studied. Records of these 12 patients were reviewed and were correlated with the neuropathologic findings available in four. The clinical diagnoses were cytomegalovirus infection (five patients), rubella (two patients), congenital syphilis (one patient), and trisomy 13 syndrome (three patients). No diagnosis was made in one infant. At neuropathologic examination, perforating medium-sized arteries to the basal ganglia and thalami had thickened hypercellular walls, with deposits of amorphous basophilic material in three infants. Results of computed tomography and radiography of brain sections were normal in these areas. Sonography is helpful in detecting early noncalcific inflammation and mineralization in vasculitis. Although nonspecific, these findings should alert the physician to the possibility of congenital infection or chromosomal abnormality.