Laser-induced fluorescence (LIF) spectroscopy combined with principal component analysis is employed to detect and quantitatively analyze frying-oil contamination in a variety of vegetable oils. Olive and peanut oils adulterated with frying oil are analyzed using LIF spectroscopy; the intensities and positions of fluorescence peaks are utilized to determine the relative concentrations of the components and the collected data is processed and analyzed by combining principal component analysis with a partial least-square model. The results show that the intensities of fluorescence peaks around 500 nm increase with increasing concentrations of frying oil, while the intensities of fluorescence peaks around 670 nm are reduced with increasing amounts of contamination. The vegetable oils are classified utilizing this methodology, and the frying-oil contaminant concentrations are predicted within 2% error.