Abstract: A method for the catalytic manufacture of MIBK and DIBK from DMK and/or IPA (optionally in the presence of water) while obtaining improved control over the ratio of DIBK to MIBK in the product stream, comprising reacting, in the presence of an aldol condensation catalyst, a reactant mixture comprising DMK and/or IPA and an effective amount of an additional reactant selected from the group consisting of mesityl oxide (MSO) and methyl isobutyl carbinol (MIBC) and mixtures thereof. Reaction temperature may also be changed to affect the product ratio obtained. The preferred catalyst is copper-based. An overall excess of hydrogen is desired, and this may be achieved by introducing or recycling hydrogen, and/or by balancing exothermic and endothermic reactions. By this invention, the product ratio of DIBK to MIBK is altered such that, as DMK and/or IPA conversion is increased, a lesser amount of DIBK than normal is produced, resulting in improved ability to control the product ratio of these materials.