The association between measurements of lateral ventricle dilatation determined by serial ultrasound and brain specific creatine-kinase isoenzyme patterns (CK-BB) is studied in 60 very low birth weight preterm neonates of 1,500 g birth weight or 32 weeks gestation or less. The patients were divided into three groups according to cranial ultrasonographic findings: Group A (n = 20) had isolated peri-intraventricular hemorrhage (PIVH); group B (n = 20) had PIVH and dilated ventricles (VM); group C (n = 20) were normal matched preterms and formed the control group. Compared to control babies or those with isolated PIVH, high serum concentrations of CK-BB were observed after birth in babies with persistent dilated ventricles at two weeks postnatal age (p less than 0.01). No difference was found between CK-BB levels of babies with isolated PIVH and control group (p greater than 0.05). We suggest that an elevated CK-BB value is found in babies with persistent ventricular dilatation suggesting severe and diffuse brain damage after post-hemorrhagic ventriculomegaly (VM).