Connatal periventricular pseudocysts are important sequelae of different noxious insults in the developing brain. Accurate diagnosis of those pathologic entities during early life has therefore become of direct concern to the clinician. Our experience with 12 infants of connatal periventricular pseudocysts provides the basis of this study. They belonged to different pathological entities: focal paraventricular pseudocysts (5 cases), subependymal pseudocyst (3 cases), connatal viral infection (3 cases), and chromosomal abnormality (1 case). When present at birth, they suggest an intrauterine pathology. It has only been with the advent of real-time cranial ultrasound that periventricular pseudocystic lesions can be detected in neonates following an abnormal pregnancy. Some obstetric complications during the second trimester can cause paraventricular or subependymal pseudocyst in the foetus. Neurotrophic viral infection and chromosomal abnormalities have also been implicated in the production of cystic lesions in this region. These lesions are not a terminal event in infants but may be a condition of major clinical importance for further neurological development.