Excess molar volumes of an aqueous solution of non-ionic surfactant n-decyl hexaoxyethene glycol monoether, {CH3 (CH2)(9)O(CH2CH2O)(6)H}, or (C10E6), have been investigated as a function of composition chi and temperature. The measurements in the high dilute region, i.e. the region in the vicinity of the critical micelle composition (c.m.c.), have been made at the temperatures (298.144, 308.141, and 318.143) K. In this study V-m(E) is negative and increases with temperature; V-m(E)(x) changes slope at chi = (1.5, 1.3, and 1.2) . 10(-5) at the temperatures (298.144, 308.141, and 318.143) K, respectively. The investigations over the whole range of x have been carried out at the temperature 298.144 K at which the aqueous solution of C10E6 in the range of chi between 0.0283 and 0.0734 creates lyotropic liquid crystals. The results for V-m(E) have been fitted to an association model and the values of the aggregation number N, Delta V-m,V-,(micell) and the critical micelle composition have been determined.