Objectives　To detect the expression of STAT3 in children with FCD (focal cortical dysplasias) type IIIa. Methods The expression of STAT3 and P-STAT3 (ser727) were determined in temporal lobe specimens from 26 children with FCD type IIIa and from 5 normal control by immunohistochemistry, immunofluorescence and Western blot. Results The expression of P-STAT3 (ser727) was obviously higher in FCD type IIIa than in control group. P-STAT3 (ser727) was located mainly in the nucleus of astrocytes. Conclusions Activated STAT3 might contribute to the patholgenesis of FCD type IIIa by mediating proliferation of astrocytes.