Background: Recently, it was reported that antipsychotic treatment reverted Contactin Associated Protein-Like 3 (CASPR3, same as CNTNAP3) mRNA expressions in leukocytes of schizophrenia (SCZ) subjects to the same levels as healthy controls. CASPR3 was expressed in various regions of the mice brain (cortex, frontal lobes, corpus callosum, hippocampus, etc.). Thus, this study evaluated CASPR3 mRNA expression in SCZ subjects to find a new clue of schizophrenia pathogenesis.Methods: One hundred SCZ subjects and 100 age-matched controls were compared. Levels of CASPR3 mRNA in leukocytes were analysed with a quantitative real-time PCR method using TaqMan probes.Results: CASPR3 mRNA expression was significantly higher in leukocytes of SCZ subjects than controls. However, there were no significant correlations between expression level and any clinical parameters in 50 SCZ subjects.Conclusion: Considering that CASPR3 is involved in building the brain neural network and autophagy in circulating leukocytes, abnormal CASPR3 expression in SCZ subjects may be associated with the pathogenesis of SCZ.