Methanesulfenyl chloride (CH3SC1) has been used frequently as a reactant, especially in the study of its addition across carbon-carbon double bonds.1–4In the course of preliminary chemical kinetic investigations of the gas phase chlorination of small sulfur containing molecules, quantitative ultraviolet spectra data for CH3SC1 were needed to calculate the rate of formation of reaction products. We report here the extinction coefficients for CH3SC1 in the wavelength region 2000 Å to 4000 Å. To our knowledge these have not been reported previously.