We analysed the level of cerebrospinal fluid (CSF) somatostatin in children with febrile seizures and epilepsy. In the febrile seizure group (n = 23), the somatostatin level was 83.9 ± 11.2 pg/ml, which was significantly higher than that of age-matched controls. CSF samples obtained within 3 h of the last seizure had higher somatostatin levels (106.1 ± 12.4 pg/ml;n = 14) than did the CSF obtained after 3 h (49.4 ± 15.6 pg/ml;n = 9). The mean somatostatin level in the epilepsy group was 35.3 ± 4.3 pg/ml (n = 34), and was distributed as follows: 27.6 ± 3.6 pg/ml in the idiopathic generalized epilepsy group (n = 16), 44.0 ± 9.4 pg/ml in the symptomatic generalized epilepsy group (n = 13), and 37.2 ± 10.1 pg/ml in the partial epilepsy group (n = 5). The levels in each group were significantly higher than those in age-matched controls. Somatostatin is a hypothalamic tetradecapeptide with excitatory effects on neurons in children with febrile seizures and epilepsy. The finding that patients with convulsive disease had elevated levels of CSF somatostatin suggests that somatostatin release is somehow related to seizure activity. It remains to be determined whether this is due to increased release from over-active excitatory neurons or leakage from damaged or anoxic neurons, secondary to seizure activity.