The object of this investigation was to determine the effects of specific adsorbed gases on the resistivity of thin titanium metal films. An experimental system was designed and fabricated to obtain reliable data by controlling all parameters which might affect the resistivity of the films. Titanium metal films were deposited in an ultra-high vacuum environment and the film resistance recorded as a specific gas was allowed to contaminate the clean film surface. Five separate investigations were made to study the effects upon the film resistivity when contaminated by air, by nitrogen, by hydrogen, and by helium. Each of these gases caused the resistance of a fresh titanium film to increase. Studies were made with previously contaminated films to clarify the nature of the gas adsorption process and relate this to the observed change in resistance. From these results and published information of related work by other authors, explanations for the observed results were proposed. Increase in resistance due to adsorption of oxygen and hydrogen was attributed to the type of chemical bonds with the surface metal atoms, which was ionic in the case of oxygen, and covalent in the case of hydrogen. The change due to nitrogen and helium adsorption was attributed to increased surface scattering of conduction electrons.