Nanometer-sized semiconductor particles (CdTe) were used as an inorganic matrix for the laser desorption/ionization mass spectrometry of fatty acids. The excitation power dependence of the peak intensity of stearic acid (Ste), [Ste - H](-), was observed, and it was proportional to the square of the excitation power. The peak intensity of [Ste - H](-) decreased by addition of a hole scavenger (KSCN). It was understood that the ionization of fatty acids were due to the biexciton Auger recombination and electron ejection from CdTe. CdTe were then loaded on zeolite surface. The peak intensity enhancement of the deprotonated ion of fatty acid were observed. This phenomenon was explained by measuring the carrier lifetime for Auger recombination in CdTe. In addition, reproducibility of fatty acid ions was highly improved reflecting homogeneous distribution of CdTe on zeolite surface. CdTe/HM20 was successfully applied to the quantitative analysis of Ste in human serum by isotope dilution using (13)C18-Ste. The concentration of Ste in human serum samples was estimated to be 76.62 mg/kg with the standard deviation (SD) of 2.37 mg/kg.