A recently described differential densimeter was used to measure the densities of Liquid mixtures of propane and cyclopropane at three different compositions, and several temperatures between T = 158 K and T = 201 K. The densimeter cell was calibrated with propane and ethane at T = 121.902 K. The differences in density between pure propane and pure cyclopropane were measured along the saturation line between T = 152 K and T = 176 K with an estimated precision of +/- 0.1% per cent. The liquid cyclopropane density was obtained, relative to the propane literature density data, in the same temperature range and with an estimated precision of +/- 0.02 per cent. The differences in liquid density between pure propane and three mixtures of propane and cyclopropane were measured between T = 158 K and T = 201 K. The compositions studied had the following approximate propane mole fractions: 0.3, 0.5, and 0.8, respectively. The excess molar volumes calculated from the experimental data decrease with temperature, and a maximum value of V-m(E) = 0.18 cm(3) mol(-1) is found for the mixture with x(C3H8) = 0.5 at T = 159 K. The estimated precision in the excess molar volumes is +/- 0.02 cm(3) mol(-l). The results for the excess molar volume are compared with the predictions of the Deiters equation of state.