The synthesis of MIBK was studied over Pt supported on NaX and CsX zeolites. The activity increased as both the temperature and the H-2/Ac ratio were increased. Temperature had also a beneficial effect on the selectivity to MIBK but the H2/Ac ratio had an opposite effect. Activities and selectivities were always higher for Pt/NaX than for Pt/CsX. For Pt/NaX, increasing the reduction temperature increased the activity but decreased the selectivity to MIBK. Both catalysts were quite stable and selectivities to MIBK of 70% were obtained over PtNaX at 613 K and H-2/Ac = 0.5. The absence of both strong acidic and strong basic sites and a proper balance between metallic and basic sites are responsible for the behavior observed.