A diffuse reflectance mid-infrared Fourier transform spectroscopy (DRIFTS) method is described for obtaining high quality Fourier transform infrared (FTIR) spectra of cements. DRIFT spectra of synthetic C 3 S, C 2 S, C 3 A, and C 4 AF and of pure gypsum, bassanite, anhydrite, syngenite, and calcite are shown. Typical spectra of American Petroleum Institute class G and class A cements display characteristic features which can be related qualitatively to variations in the constituent minerals. For quantitative analysis, the FTIR spectra of 156 cements of varied origin and known elemental composition have been used to construct multivariate calibration models. These relate the spectrum to composition (expressed in terms of nine mineral components and five minor oxides) and allow the composition of unknown cements to be determined rapidly from the FTIR spectrum alone. Error estimates are given.