Esterification of tert-butanol by acetic anhydride, a typical acid-base catalytic reaction, was conducted with excellent selectivity and high yield in a neutral ionic liquid [BMIm]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate). Many other tertiary alcohols could also be successfully converted to the corresponding esters in [BMIm]BF4. Separation of product and recovery and reuse of ionic liquid are all convenient in this system. Here, the need for catalysts is avoided through the use of catalytically active ionic liquids as solvents. (c) 2005 Elsevier B.V. All rights reserved.