Densities of 1-pentanol aqueous solutions were measured by using a vibrating tube densimeter especially designed and equipped to perform accurate measurements from ambient conditions up to T=423 K and p=80 MPa. The densimeter was tested by measuring densities of NaCl (ag). A comparison with the most reliable literature data showed very good agreement with differences lower than (0.03 and 0.1) kg . m(-3) for molalities below and above 0.5 mol . kg(-1), respectively. From the density measurements the apparent molar volumes of 1-pentanol in water V-phi were determined as a function of molality m at temperatures from T=298 K to T=413 K at p=0.1 MPa and p=19 MPa. At a given temperature and pressure, the partial molar volume of 1-pentanol at infinite dilution V-phi(0) was calculated by a linear fit to the V-phi against m data. V-phi(0) increases with the temperature at both p=0.1 MPa and p=19 MPa and it shows a negative pressure dependence in the whole investigated temperature range. The temperature and pressure dependence of V-phi(0) is consistent with the hydrophobic nature of 1-pentanol.