Optical rotary dispersion spectra have been studied of methylene blue complexes of glycosaminoglycans and different derivates of chondroitin 4-sulphate (free and protein bound complexes of different molecular weights and degrees of sulphation). Structural requirements of Ch-4S induction of the extrinsic Cotton effect in methylene blue were formulated. This Cotton effect is supposed to reflect the right-handed helical structure of the polysaccharide molecules. Ch-4S displayed induced Cotton effect both in free and in protein bound form; molecular weight should exceed 2-3000 (at least 4-6 disaccharide units), degree of sulphation should exceed 3% sulphate-sulphur content (more than 0.5 sulphate per one disaccharide unit). For comparison the effect of different derivatives of Ch-4S on the rate of in vitro collagen fibril formation was investigated. Close correlation was found between the macrostructural characteristics and the possible biological effect of Ch-4S. The biological significance of the macrostructural properties of Ch-4S is discussed.