Adhesion of micro-organisms to surfaces in marine environments leads to biofouling. The deleterious effects of biofilm growth in the marine environment are numerous and include : energy losses due to increased fluid frictional resistance or to increased heat transfer resistance, risk of corrosion induced by micro-organisms, loss of optical properties, quality control and safety problems. Antifouling agents are generally used to protect surfaces from being affected by such a biofilm. These agents are toxic and can be persistent, causing harmful environmental and ecological effects. Moreover, the use of biocides and regular cleaning considerably increase the maintenance costs of marine industries. An improved knowledge of the biofilm adhesion mechanisms is needed for the development of an alternative approach to the currently-used antifouling agents. The aim of this study is to characterise the chemical composition of the molecules first interacting with stainless steel during the period immediately following immersion in natural seawater and to elucidate the kinetics of the adsorbtion process. Proteins are shown to adhere very rapidly, closely followed by carbohydrates. The distribution on the surface of the organic molecules is also examined. The adsorbate on the surface is not so much a continuous film as a heterogeneous deposit, whose average thickness varies widely. The cleaning procedures used affect the adsorption kinetics. In particular, cleaning with hexane results in slower adsorption of nitrogen-containing species than does cleaning in acetone.