Two children, aged 2 weeks and 2 months, with multicystic encephalomalacia aer described. Although computerized tomography (CT) scan was used for the diagnosis, the value of the simple method of transillumination is stressed. The mother of one child had mumps with meningitis at 26 weeks' gestation. The other child had an echovirus 11 isolated from the cerebrospinal fluid and herpesvirus hominis (HVH) from the skin at 8 weeks. We speculate that the changes in the brains of these babies may be due to the respective viruses causing a fetal encephalitis.