Abstract： Objective To investigate the contents of IL-1β and IL-1ra in cerebrospinal fluid of children with Japanese encephalitis, and their clinical significance. Methods Enzyme linked immunosorbent assay (ELISA) was employed to detect IL-lβ and IL-lra contents in 50 children with Japanese encephalitis and 20 children without nervous system disease (controls). Results IL-1β contents in climax stage, convalescent stage and the controls were (49. 43±14. 59) , (24. 73±14. 50) and (8. 98± 1.26)μg/L (F = 79.88, P<0.01); IL-lra contents in climax stage, convalescent stage and the controls were (177. 39±60. 19), (78. 24±44. 63) and (21. 09±3. 10) μg/L (F = 91. 53, P <0. 01). There were significant differences on IL-lβ and IL-lra contents among children with mild, moderate and severe encephalitis (climax: F = 82.36 and 66.50, P<0.01; convalescence; F = 55. 17 and 79.50, P<0.01). IL-1β content was positively correlated with IL-lra in both climax and convalescent stages (climax; r = 0. 815, P < 0.01; convalescent; r= 0.728, P < 0.01). Conclusions IL-lβ and IL-lra contents in cerebrospinal fluid are significantly increased in children with Japanese encephalitis in climax stage, which are closely correlated with the disease severity. The two indicators may participate in the pathological process of brain damages with Japaness encephalitis.