The thermodynamics of He3and He4solutions is considered for temperatures and concentrations for which the solution does not show superfluidity. Calculations of the excess chemical potentials from the experimental vapor pressure data have been carried out between 1°K and 2°K by Roberts and Swartz. It is found that while the behavior of the He3component can be reasonably explained down to 1°K within the framework of the classical solution theories, no such agreement is obtainable for the He4component. The discrepancy is explained by extending some general thermodynamical considerations of Gorter regarding pure He4to the solution. Further it is found that with a suitable choice of the Gibbs free energy expression of pure He4a satisfactory quantitative agreement is also obtainable along these lines.