The over-drainage of CSF after shunt implantation, particularly when the patient is in the vertical posture, is well documented. Problems associated with it are negative pressure syndrome (postural headache and postural irritability), abnormal skull size, craniosynostosis and subdural haematoma. The pressure gradient in the vertical position between the cranial cavity and the right atrium is 15 to 20 cm of water and between the cranial and peritoneal cavity it is 25 to 32 cm of water and both these are much higher than those needed for the optimum functioning of a conventional shunt. The need, therefore, has been for a self-regulating device that can adjust itself to any change of posture from horizontal to vertical and vice versa and regulate the flow of CSF from the cranial cavity. "Z" Flow hydrocephalus shunt system has this in-built self-regulating mechanism to prevent over drainage of CSF and the resultant abnormal low pressure in the cranial cavity. The rationale behind the functioning of "Z" Flow hydrocephalus shunt system has been discussed, its design has been described and illustrated and the results of pressure monitoring after Z Flow shunt implantation in five adult patients have been detailed. As the opening pressures of the "Z" Flow shunt system are 15-29 cm of water, it has been found to prevent over-drainage of CSF and maintain intraventricular pressure within normal limits.