The hydrodynamic characteristics in aqueous solution at ionic strength I = 0.2 M of carboxymethylchitins of different degrees of chemical substitution have been determined. Experimental values varied over the following ranges: the translational diffusion coefficient (at 25.0 degrees C), 1.1 < 10(7) x D < 2.9 cm(2) s(-1); the sedimentation coefficient, 2.4 < s < 5.0 S; the Gralen coefficient (sedimentation concentration-dependence parameter), 130 < k(s) < 680 mL g(-1); the intrinsic viscosity, 130 < [eta] < 550 mL g(-1). Combination of s with D using the Svedberg equation yielded ＇sedimentation-diffusion＇ molecular weights in the range 40 000 < M < 240 000 g mol(-1). The corresponding Mark-Houwink-Kuhn-Sakurada (MHKS) relationships between the molecular weight and s, D and [eta] were: [eta] = 5.58 x 10(-3) M-0.94; D = 1.87 x 10(-4) M-0.60; s = 4.10 X 10(-15) M-0.39. The equilibrium rigidity and hydrodynamic diameter of the carboxymethylchitin polymer chain is also investigated on the basis of wormlike coil theory without excluded volume effects. The significance of the Gralen k(s) values for these substances is discussed.