A technique called ‘Near Infrared diffuse reflectance spectroscopy’ is able to monitor the moisture content in resin rich fiber reinforced composite surfaces and the cure state of resin at the surface of a resin rich fiber reinforced composite. Measurement of water in composites made from 934 resin and T300 fibers was addressed using both normalized absorption spectroscopy and using a “Chemometrics” second derivative partial least squares spectrum analysis. (Chemometrics is the procedure of relating measurements made on a chemical system via application of mathematical or statistical methods). We will show that interpretation of a diffuse reflectance near IR spectrum is more complex than interpretation of a transmission near IR Spectrum, with the result that a partial least squares (Chemometrics) analysis gives better results than a straightforward normalized Beer type plot. Calibration curves have been produced to relate diffuse reflectance near IR spectra to water content for uptake and desorption of water in medium and high performance epoxy resins, high performance adhesives, and carbon fiber reinforced composites. Calibration curves have also been produced to relate the near IR diffuse reflectance spectrum to cure state in high performance adhesives and carbon fiber reinforced composites.