Hydrogenation of gamma-valerolactone to 1,4-pentanediol was performed over both precious and base metal catalysts in a continuous flow reactor under H-2 pressure. Cu/ZnO catalyst showed the highest catalytic performance for the formation of 1,4-pentanediol from gamma-valerolactone. Low reaction temperatures such as 140 degrees C were preferable for achieving 1,4-pentanediol, and high temperatures led to the further conversion of 1,4-pentanediol to 2-methyltetrahydrofuran and 1-pentanol. High H-2 pressures and moderate H-2 flow rates such as 90 cm(3) min(-1) were effective for the formation of 1,4-pentanediol. Calcination temperature of Cu/ZnO significantly affected its catalytic activity. A Cu/ZnO catalyst with a Cu metal loading of 40 wt.% gave the gamma-valerolactone conversion of 82.3% with the 1,4-pentanediol selectivity of 99.2% at 140 degrees C under 1.5 MPa of H-2 pressure, while no decrease in the catalytic activity was observed for 10 h.