A capillary electrophoresis method with in-column light-emitting diode induced fluorescence detection is described for simultaneous determination of D,L-serine in the midbrain of a Parkinson's disease mouse. D,L-Serine was derivatized with fluorescein isothiocyanate, and chiral separation and determination of D,L-serine derivatives were performed on a laboratory-built capillary electrophoresis system with in-column light-emitting diode induced fluorescence detector using gamma-cyclodextrin as chiral selector. Using this method, the levels of D- and L-serine in the midbrains of Parkinson's disease mice were determined. When compared to controls, the levels of D- and L-serine showed significant differences. The result suggested that the biosynthesis and the transportation of endogenous D,L-serine may participate in Parkinson's disease pathogenesis.