Objective    To explore the mechanism of arginine vasopressin (AVP) in the onset of febrile convulsion.     Methods    Radioimmunoassay (RIA) was used to determine plasma AVP levels in 24 children with complicated febrile convulsion

32 children with simple febrile convulsion

20 children with upper respiratory infection

and 18 normal children. Their plasma sodium ion and plasma osmotic pressure were measured at the same time.     Results    AVP level in complicated febrile convulsion group and simple febrile convulsion group was significantly higher than upper respiratory infection group and control group (P<0.05)

and the level was higher in complicated febrile convulsion group than in simple febrile convulsion group (P<0.05). Plasma sodium ion and plasma osmotic pressure were lower in complicated febrile convulsion group than the other 3 groups significantly (P<0.05)

and there was no significant difference among other groups. There was a positive correlation between the levels of AVP and temperature(P<0.05).      Conclusion    Determining plasma AVP level is conductive to identify the type of febrile convulsion. AVP can decrease the threshold of febrile convulsion and increase the susceptivity of convulsion. AVP may play an important position in the onset of febrile convulsion.