The compressibility of acetone has been redetermined at temperatures of 25 to 55 °C, and at pressures from atmospheric to 1 kbar. The results have been fitted to the Tait equation, and values of (∂P/∂T)V and of the internal pressure have been calculated. The heat capacity at constant volume has also been deduced as a function of pressure and temperature. The variations in these and other derived quantities have been shown to lead to conclusions about structural changes in the liquid.