In the presence of lysolecithin at physiological pH it was found that the increase of ionic strength facilitates the adhesion of hen erythrocytes. In this medium, dibutyryl cyclic adenosine monophosphate (DBcAMP) increases the adhesion index of the cells. If the osmotic pressure is elevated without a proper increase of ionic strength, the lysolecithin induced hemolysis and adhesion are found to be lacking.