A refractively scanned system for Fourier transform infrared spectroscopy (FT-IR), the Perkin-Elmer Model 1500 FT-IR, is described. The components and geometry of the instrument are presented diagramatically. The interferometer uses pathlength scanning mechanics to encode each of the spectral components into a data record called an interferogram. A fast Fourier transform processes the data, yielding an infrared spectrum in a few seconds. An available cooled mercury cadmium telluride detector enhances the signal to noise ratio. Experiments are described which illustrate the technique's application.