Seizure frequencies will be recorded daily for the 4-week baseline period and the 3 month study period. At the end of the 3 month study period, the number of seizures in the preceding 28 days will be used to calculate the mean seizure number, which will be expressed as a percentage of the mean baseline number of daily seizures (ie, the number of seizures during the 4 weeks before the child started either the diet or the control phase of the study).No changes will be made to the child's antiepileptic medication during the 4-week baseline or the 3-month study periods, unless medically indicated; e.g. drug side effects, or status epilepticus; in which case standard therapy will be provided.