OBJECTIVES: Isolated paraventricular cysts detected on routine cranial ultrasonography in premature and full term neonates are often incidental findings. The aetiology and clinical significance of these lesions is uncertain. A case control study was designed to attempt to clarify the clinical significance of isolated paraventricular cysts in terms of growth and neurodevelopment. METHODS: Ten infants with isolated paraventricular cysts on neonatal cranial ultrasonography were identified. These were matched with 10 control infants for sex, gestational age and birthweight. All infants were assessed at a corrected age of 18-31 months for growth and neurodevelopment. Two index infants and their controls were excluded from analysis of psychometric data as the neurodevelopmental assessment tools used were different. RESULTS: There was no statistically significant difference between the index and control groups in terms of growth, motor and psychometric assessment at follow up. CONCLUSIONS: The study suggests that isolated paraventricular cysts detected on routine cranial ultrasonography have no prognostic significance. However the study involved a small sample size with limited power of study (power = 0.3). A larger prospective cohort study would help to clarify the clinical significance of this condition.