Fourteen children with repeated transient or sustained cerebrospinal fluid shunt dysfunction and with markedly increased intracranial pressure are presented. In all cases, the lateral ventricles had become very small soon after the insertion of a shunt valve that opened at a low pressure, but symptoms of shunt dysfunction did not occur until 6 months to 12 years later. The raised intracranial pressure was treated by subtemporal craniectomy alone (12 patients) or in combination with elevation of the shunt valve opening pressure (2 patients). Subtemporal craniectomy alone was sufficient to alleviate moderately increased intracranial pressure, but both methods were required when the pressure rise was severe. The high intracranial pressure is accompanied by impairment of the drainage of ventricular fluid, which is caused by collapse of the walls of the lateral ventricles around the proximal shunt catheter. But the sequence of events that leads to the severe rises in intracranial pressure characteristic of this syndrome is poorly understood. The possibility that an inflammation-mediated brain swelling arising from mild systemic infections might further compromise already small ventricles and precipitate shunt dysfunction is suggested.