This review mainly focuses on the principal, instrumentation, interpretation, application of infrared spectroscopy. Infrared (IR) radiation refers broadly to that part of the electromagnetic spectrum between the visible and microwave region. Of greatest practical use to the organic chemist is the limited portion between 4000 and 400cm -1. Infrared spectroscopy monitors the interaction of functional groups in chemical molecules with infrared light resulting predictable vibrations that provides a “fingerprint” characteristic of chemical or biochemical substances present in the sample. Infrared spectroscopy is a technique that probes the vibrations within a material. Infrared spectroscopy has always been a powerful tool for the identification of organic materials. The development of Fourier transform infrared (FTIR) spectroscopy has introduced a popular method for the quantitative analysis of complex mixtures, as well as for the investigation of surface and interfacial phenomena. Key words: IR Spectroscopy, Detectors, Polyatomic molecules, Stretching Vibrations, Bending Vibrations.