The use of air-gap membrane distillation for the selective removal of propanone from aqueous solutions was tested. The effect of the following operating conditions upon flux and selectivity was experimentally examined: feed concentration, feed flow rate, feed temperature, and coolant temperature. Although the PVDF membranes tested performed well at the propanone feed concentrations encountered in fermentation processes, they demonstrated wetting limitations at higher concentrations. Within the feed temperature range of 40-70 degrees C, and propanone concentration up to 6 wt%, propanone selectivities of 2-6 were achieved. A mathematical model of the process was developed and validated.