The goal of this study was to investigate reliable cognitive change in epilepsy by developing computational procedures to determine reliable change index scores (RCIs) for the Dutch Wechsler Intelligence Scales for Children. First, RCIs were calculated based on stability coefficients from a reference sample. Then, these RCIs were applied to a sample of 73 children with refractory epilepsy who were tested twice with the WISC-RN[superscript NL]/WISC-III[superscript NL] after a mean interval of 2.3 years. Results indicated that children with refractory epilepsy are at risk for cognitive decline over time: 26.0% of the children showed reliable losses on Verbal IQ and 16.4% on the full scale IQ (expected rate = 5%). Declines on performance IQ were within expected limits.