Fecal lipid content is usually determined by titrimetric or gravimetric methods, but these methods are time consuming and involve dangerous solvents. We have developed a new method of measuring fecal lipids by Fourier transform infrared spectrometry (FTIR) with an attenuated total reflectance accessory that is fast and requires no solvents. The spectra of stools from 4000 to 750 cm-1 were analyzed, and the lipid concentrations were measured by using a calibration curve prepared by partial least-squares analysis of data from 34 stools. The linearity of the method was tested by mixing low-lipid stools with lipid-overloaded stools to give a range of 0.5-15% lipid. The prediction residual values were -0.49-0.78% for calibrators, and -2.55-2.34% for unknown samples. There was good agreement between the fecal lipids measured by gravimetric (x) and FTIR (y) methods:y = 0.87x + 5.5. The standard error of prediction was 1.07%.