The effects of pH, salt concentration, and temperature on the adsorption of a water-soluble insect cuticular protein to chitin have been investigated. The adsorption is dependent upon pH, decreasing rapidly as the pH increases from the region of the isoelectric point of the protein. Increase in salt concentration decreases adsorption but the adsorption appears to be little influenced by changes in temperature. Tyrosine-rich protein fractions are preferentially adsorbed. The adsorption is partly irreversible and an increase to pH 9 is necessary before all the adsorbed protein can be removed. It is concluded that there is only a weak bonding between the chitin and the water-soluble cuticular protein.