Previous studies in children have shown a strong correlation between raised intracranial pressure (RICP) and the Gosling pulsatility index (PI) as determined by transcranial Doppler ultrasonography (TCD). This diagnostic modality can, therefore, be used as a non-invasive method for the indirect evaluation of shunt function in children with hydrocephalus. Transcranial Doppler waveform analyses were done in 15 children with hydrocephalus, before and after insertion of a ventriculo-peritoneal shunt. All had clinical evidence of raised intracranial pressure (ICP) prior to surgery. CT had demonstrated dilated ventricles and, in some, additional features of RICP. Fifteen children without clinical and CT evidence of hydrocephalus were examined in an identical manner to act as a control group. The results clearly demonstrated that TCD may be a useful, non-invasive means of assessing the need for a cerebrospinal fluid (CSF) diversionary procedure and also for follow-up and monitoring.