The unperturbed chain dimensions of atactic near-monodisperse poly(ethylethylene) were evaluated in different Theta-solvents over the temperature range 10-80 degrees C. Radii of gyration, measured by small angle neutron scattering (SANS), were found to increase with increasing temperature and led to a value of 0.4 x 10(-3) deg(-1) for d ln [R(2)](0)/dT; behavior which replicates that seen in the melt state via SANS and thermoelastic measurements. Those findings are contrary to those from intrinsic viscosity measurements.