An 8-m thick Cuprophane hollow-fibre membrane not only had a higher ultrafiltration coefficient than an 11-m thick membrane but was more permeable and selective for ethanol dialysis and extract removal from beer. Transmembrane pressures above 40 Pa did not affect alcohol removal but did prevent further extract removal and therefore improved the final beer quality. To achieve selective removal of alcohol, beer flow rates must be above the critical velocities but remain below values which would require too great a membrane area.