The discovery of thermophilic Archaea was one of the major scientific events of the last years, especially because their enzymes are of great interest. Effectively, these later concern numerous biotechnological applications such as the enzymatic starch-hydrolysis in glucose production. In this review, we examine the different thermophilic archaeal amylolytic enzymes already characterized, with particular attention to alpha-amylases, the most studied enzyme of the glycoside-hydrolase family. The ecological importance of these enzymes, as well as their biochemical properties, their structure, and their evolutionary relationships are described. (C) 2000 Elsevier Science Inc. All rights reserved.