Temperature dependences of the conformational properties of sodium-type gellan gum in aqueous solutions were studied by osmometry. The measurements were carried out in the range from 25 to 45 degrees C for aqueous solutions of three sodium chloride concentrations (C-s = 25, 50, and 75 mmol dm(-3)). It was found that the M(n) values obtained at 45, 40, 36, 28, and 25 degrees C with different C-s agreed with each other and the average M(n) values above 36 degrees C were almost half the values obtained at 28 and 25 degrees C, suggesting association of two molecules. The values of A(2) obtained at 45, 40, 36, 28, and 25 degrees C were almost the same at each C-3, while these A(2) values decreased with increasing C-s. The M(n) value obtained in solution with C-s = 25 mmol dm(-3) at 32 degrees C was slightly higher than those obtained above 36 degrees C but lower than those obtained below 28 degrees C, and in solutions with C-s = 50 and 75 mmol dm(-3), M(n) values could not be determined due to abnormality of the pi/c vs c plots. This suggests that a unimer should be in simultaneous equilibrium with a dimer. The data obtained at 32 degrees C were analyzed by employing a simple unimer/dimer equilibrium model. The equilibrium constant K increases with increasing C-s, which means that the extent of association increases and the proportion of dimer also increases with increasing C-s.