OBJECTIVE: To study the effect of brain damage induced by repeated febrile convulsions (FC) during early life in rats. METHODS: Sixty five 16 d rats were randomly divided into two groups: normal control group (n=15) and warm water treated group (n=50), and the latter was further divided into FC and non FC groups. The rat FC model was developed by warm water immersion (45℃). The memory capacity was tested by using a Morris water maze method. Neuronal changes were detected by thionine stain, TUNEL stain and electron microscopy. RESULTS: The searching plat form latency of rats with FC was significantly longer than that of the normal controls [( 8.33 ± 9.83 ) s vs ( 4.00 ± 2.96 ) s; P< 0.01 ]. The number of TUNEL positive neurons significantly increased in the FC group compared with that of the normal control and non FC groups [( 9.67 ± 5.52 ) vs ( 5.08 ± 4.12 ); ( 9.67 ± 5.52 ) vs ( 3.17 ± 3.35 ), both P< 0.05 ]. The mitochodrion changes, manifesting as swelling, ridge unclear or disappeared and vacuolar appearcance, were found electron microscopically, whereas no significant change was demonstrated by thionine stain. CONCLUSIONS:Repeated FC may induce brain damage in immature rats.