Results of pervaporation experiments are reported for the dehydration of two different mixtures : a ternary synthetic mixture containing acetone, methylisobutylketone (MIBK) and water and a so-called product mixture consisting of 50-60 wt% acetone 40-30 wt% MIBK 7-8 wt% water and 3-2 wt% by-products as directly obtained from a MIBK production plant. The pervaporation experiments have been carried out with PVA composite membranes of different degrees of crosslinking and two different types of TexSep composite membranes. The influence of feed composition, permeate pressure and temperature on the separation characteristics has been investigated. Especially the highly crosslinked PVA-1001 membrane yields high water concentrations in the permeate and fluxes good enough for practical application. The pervaporation results for the PVA-1001 membrane obtained with a laboratory test cell are compared with results obtained in a pilot unit. Two possibilities for integrating a pervaporation unit in a process for the synthesis of MIBK are discussed in detail.