Densities of binary supercritical mixtures of ethane with cosolvents, ethanol, 2,2,2-trifluoroethanol, and 1,1,1,3,3,3-hexafluoro-2-propanol, have been measured by a constant volume apparatus. Measurements were made in the range 0.7 to 2.0 mol % cosolvent and at pressures from 49.8 to 105.7 bar at 308.2 K. Despite the low cosolvent composition, all mixture densities deviate significantly from the density of pure ethane in the highly compressible region. Mixture densities calculated by the PR-EOS give only a qualitative representation of the experimental data.