The interaction between bovine atelocollagen and a high molecular weight fully deacetylated chitosan has been studied. Considering the apparent mass of an anionic equivalent of collagen and the results of various techniques (potentiometry, conductometry and IR spectroscopy), a purely electrostatic mechanism is demonstrated. The role of charge density and chain length of collagen chains is discussed, and although the interaction is weak and hindered by gel formation in collagen solutions, a polyanion-polycation complex is obtained. Circular dichroism spectroscopy experiments show an organization in the solid state of the complex which is quite different to those of collagen and chitosan.