Hydrogen sulfide (H2S) is corrosive to downhole and topside oil and gas production facilities. Its presence in natural gas is also limited to very low levels due to sales specifications. One alternative to control the levels of H2S and mitigate its effects in oil and gas production facilities is the injection of liquid H2S scavengers at suitable points in the system. Liquid scavengers react with H2S to form stable water- or oil-soluble reaction products. The effects and performance of H2S Scavengers with various operational parameters (i.e. type of crude water cut temperature contact time and flow pattern) are not completely understood. A laboratory testing protocol and experimental equipment were designed and constructed in order to: (1) evaluate the performance of H2S scavengers under simulated multiphase flow field conditions and (2) facilitate the selection of commercial products to be injected into oil lines through a gas-lift system and/or through umbilical lines. The approach was based on a combination of two different methodologies that combined gave an overall picture of the performance of a scavenger in a given condition. One methodology was used for initial screening of chemicals performance under different conditions and the other determined reaction kinetics under multiphase flow conditions based on the Continuous Stirred Tank Reactor concept The performance was characterized not only by the efficiency in removing H2S from the gas phase when injecting to a multiphase flow but also in terms of the kinetics of the reaction. The major achievement of this work was the development of a testing and simulation approach to select the best chemical treatment and optimal doses minimizing the cost and uncertainties associated with field trials particularly when production conditions change. Some technical contributions to the current state of the art are: An improved design of downhole chemical treatment protocols through gas lift or umbilical lines. An improved understanding of the impact of operational parameters on the efficiency of H2S sequestration in production fluids. A unique testing apparatus and computer model for the study of H2S scavenger kinetics as a tool for the optimization of downhole chemical treatment for off-shore production.