The use of tristriphenylphosphinerhodium chloride as a soluble catalyst for hydrogenation has been further investigated, and some of its specificities have been examined in systems containing more than one double bond. Its properties include the ability to add deuterium specifically to the double bonds of cyclohexene, oleic and linoleic acids, and ergosterol without introduction of additional labelling. Some hydrogenations without hydrogenolysis have been carried out (that of ω-nitrostyrene into phenylnitroethane and of cinnamyl chloride in part into phenylpropyl chloride).