Catalytically active Langmuir-Blodgett films of a rhodium complex were prepared and characterized to determine the possible effect of the molecular order of metal complexes on catalytic activity. The hydrogenation oi carbon-oxygen double bonds was used as a model reaction. The complex in solution exhibited low catalytic activity, whereas ii was highly active in the film. The catalytic activity was found to be highly dependent on the orientation of the complex within the film. The reactions were also highly selective with regard to the substrate. These observations and the observed rate dependence on temperature strongly implicate the molecular order of a metal complex as an important dimension in catalysis.