Prothrombin is expressed in the central and peripheral nervous systems. However, the mechanism responsible for the activation of prothrombin to thrombin by the activated form of factor X in the central and peripheral nervous systems remains to be explored. Here, we investigated the expression of factor X mRNA in the brain and some cell lines derived from the central nervous system. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated the expression of mRNA encoding factor X in the rat brain, A172 (human glioblastoma) and GOTO (human neuroblastoma) cells. The sequences of PCR-derived fragments were identical to those reported for rat and human factor X. These results indicated the synthesis of factor X in the cells of the central nervous system.