Monolayer properties of interfacially active fractions in six different North Sea crude oils have been studied. The fractions were separated by a consecutive adsorption procedure utilizing functionalized silica as adsorbent. The molecular weight of the fractions are between 950 and 1450 g mol - 1. They are built up of carbon and hydrogen to 99 mol% and of nitrogen, oxygen and sulfur to 1 mol%. The fractions form monomolecular films in the air/water interface. The films enter the highly compressible liquid expanded state at specific areas in the rage of 0.20-0.28m2mg-1 lytes, pH, temerature and chemical additives is reported. It is shown that aromatic solvents strongly interact with the film hence modifying its monolayer properties. Relaxation studies of strongly interact with partly water-soluble groups. Correlation between the monolayer properties of these fractions and their ability to stabilize water-in crude oil emulsions is undertaken.