The use of synthetic peptides in the goal of developing a new, inexpensive vaccine against hepatitis A virus is one of the encouraging approaches followed by many laboratories. These peptides have to be well characterized, being their physicochemical properties one of the most relevant points to control. In that sense, one can consider the study of the peptide interaction with lipid monolayers by means of the Wilhelmy plate method, to gain insight into the possible mechanism of action at the membrane level. The peptide chosen corresponds to the lineal epitope of hepatitis A virus VP3(110-121). As far as the lipids used are concerned, they were selected according to the composition of hepatocytes and erythrocytes because these structures seem to play an important role in hepatitis proliferation and infection. The peptide was able to accommodate into lipid monolayers. Interaction was slightly lower in the hepatocyte model than in the erythrocyte model, probably due to the presence of cholesterol in the hepatocyte membrane. Copyright 1999 Academic Press.