Abstract.Results of light scattering and small angle neutron scattering experiments with a 2-butoxyethanol (2-C4E,)/D20 mixture of critical composition (stoichiometric mole fraction of 2-C4E, x: = 0.0598; critical temperature T,(visual) = 42.714"C) are reported. They are carried out with the aim to find out whether the temperature dependence of the correlation length ( characterizing the extension of concentration fluctuations near T, is different from that characterizing the size of aggregates of the 2-C4E, molecules which appear to exist at temperatures away from T,. The experiments show that the temperature dependence of ( near T, is the same as that away from T, within the uncertainty of the measurements. -As a by-product of this study, neutron scattering data were collected corresponding to a wide range of values of the scaling variable x (3 < x < 2100, x = q(; q is the absolute value of the scattering vector). They are analysed in terms of the limiting form of the universal correlation scaling function g , ( x ) = C , x -( 2 -9 ) to determine the value of the universal critical exponent q. A value of q = 0.039~0.004 is found. It is considered consistent with the theoretically expected values.