Objective Malformations of cortical development (MCDs) represent a well-recognized cause of intractable epilepsy.Bone morphogenetic proteins (BMPs) are members of the transforming growth factor (TGF) superfamily of cytokines.The aim of this study is to define the expression and the cellular distribution of BMP-4 in focal cortical dysplasia (FCD) type Ⅱb and tuberous sclerosis complex (TSC).Methods We have studied surgically resected tissues from 19 patients, 12 FCD Ⅱb and 7 TSC.Normal-appearing control cortex/white matter was obtained at autopsy from 5 patients without a history of seizures or other neurologic disease.Western blot and immunocytochemistry were performed.Results Western blot analysis showed that there was a statistically significant decrease of BMP-4 protein level both in MCD comparison with CTX.Immuno-staining results showed that moderately-strongly staining was widely observed in neurons and glial cells in CTX.In dysplasia cortex of FCD Ⅱb, BMP-4 was widely expressed in normal-appearing neurons and reactive astrocytes, more intensely expressed in giant neurons (GNs), dysplastic neurons (DNs) and balloon cells (BCs).In cortical tubers, it showed similar features with FCD Ⅱb.Conclusion The reduced expression and specific cellular distribution of BMP-4 suggested a possible contribution of BMP-4 to the dysplasia cortex of these malformations of cortical development.